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Commit 15d24d8d authored by Sanders, Austin Ray's avatar Sanders, Austin Ray
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Added docs and assets for camera geometry and projection

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## Introduction
-----
In order to access and view the geometry for an ISIS image cube \[raw
instrument camera cube, (i.e., PDS-EDR)\], the application
[**spiceinit**](http://isis.astrogeology.usgs.gov/Application/presentation/Tabbed/spiceinit/spiceinit.html)
must be **successfully** applied to the cube. Once **spiceinit** has
been applied, there are a number of applications that will be able to
compute and output statistics about your image based on the raw **Camera
Geometry** .
## Camera Geometry
-----
**Camera Geometry** refers to the viewing geometry of an observation. It
also implies a 'non-projected' cube (sometimes referred to as a Level1,
though it does not require radiometric calibration).
!!! Note "Within the ISIS environment, unless otherwise specified, **ALL** applications default (for input and output) to the following geometric reference (regardless of target body):"
- **Longitude\_Domain = 360** \[Longitudes will be reported in the
range of 0 to 360 degrees (not -180 to 180)\]
- **Latitude\_System = Ocentric** \[Versus Ographic; Note: there is
not difference for a spherical body\]
- **Longitude Direction = East** \[Longitude values increase to the
east\]
Definitions for the geometric reference terms can be found in [Learning
About Map Projections](concepts/Learning About Map Projections)
## Camera Information Applications
-----
### **Camstats**
For a given image cube, the application
[**camstats**](http://isis.astrogeology.usgs.gov/Application/presentation/Tabbed/camstats/camstats.html)
will report Minimum, Maximum, Average and Standard Deviation for the
following:
**Geometric Information**
- Latitude
- Longitude
- Resolution, LineResolution, SampleResolution
- AspectRatio
**Photometric Information**
- Phase Angle
- Emission Angle
- Incidence Angle
- LocalSolarTime
- NorthAzimuth
Example (not all parameters shown):
camstats from=xxxx.cub linc=1 sinc=1
!!! Note " The *linc* and *sinc* parameters default to 1. For larger pixel size images, such as HiRISE or CTX data, setting the *linc* and *sinc* values to higher values (10, 100) would help the application to run faster. Set with care knowing that the application is literally skipping line/sample data to retrieve SPICE information."
- **camstats** supplies useful information that can be considered and
applied when map projecting images (Level2 processing).
### **Mosrange**
Given a list of multiple raw image cubes, the application
[**mosrange**](http://isis.astrogeology.usgs.gov/Application/presentation/Tabbed/mosrange/mosrange.html)
computes the range of latitude/longitude and resolution statistics for
all images given.
Example (not all parameters shown):
mosrange fromlist=list_of_lev0_w_spice.lis to=output_map_information.map projection=Equirectangular
- This is one application that allows the user to specify output
latitude type, longitude direction and longitude domain.
- Knowing the information about your set of images at this point is
useful, especially if the goal is to generate a mosaic. The output
can be used later in defining the desired output map projection in
Level 2 processing.
### **Campt**
The application
[**campt**](http://isis.astrogeology.usgs.gov/Application/presentation/Tabbed/campt/campt.html)
will supply geometric and photometric information based on a *single*
latitude/longitude value (remember the raw camera geometry defaults when
entering values) or a *single* line/sample coordinate of an image cube.
**Geometric Information**
- Latitude
- Longitude
- Resolution
**Photometric Information**
- Phase Angle
- Emission Angle
- Incidence Angle
**In addition** , this application will return a list of other
spacecraft, sun and instrument related information such as:
- SpacecraftPosition
- SpacecraftAzimuth
- SubSpacecraftLongitude
- SubSolarLatitude
- SubSolarLongitude
- Time information (EphemerisTime, UTC)
Example (not all parameters shown):
*Enter lat- [](fixit.wr.usgs.gov)* [*Ocentric* **](fixit.wr.usgs.gov)
*/long- [](fixit.wr.usgs.gov)* [*360* **](fixit.wr.usgs.gov) *point
location*
campt from=xxxx.cub latitude=0.0 longitude=270.0 type=ground
or
Example (not all parameters shown):
*Enter line/sample pixel location-current default of application*
campt from=xxxx.cub line=512 sample=512 type=image
### **Phocube**
[**phocube**](http://isis.astrogeology.usgs.gov/Application/presentation/Tabbed/phocube/phocube.html)
will compute and generate a separate output [multi-band ISIS
cube](https://DOI-USGS.github.io/ISIS3/gh-pages/ISIS_Cube_Format.html) where each band will represent the selected
(parameter=TRUE) geometric and photometric elements. The bands are named
appropriately in the output cube labels: **Group=BandBin** .
```
Object = IsisCube
Object = Core
StartByte = 65537
Format = Tile
TileSamples = 128
TileLines = 128
Group = Dimensions
Samples = 1024
Lines = 1024
Bands = 6
End_Group
Group = Pixels
Type = Real
ByteOrder = Lsb
Base = 0.0
Multiplier = 1.0
End_Group
End_Object
Group = BandBin
Name = ("Phase Angle", "Emission Angle", "Incidence Angle", "Latitude", "Longitude")
End_Group
```
- **phocube** requires a successful **spiceinit** execution
- **phocube** can be applied to an unprojected "Level1" image cube or
an individual map projected "Level2" image.
- **phocube** will not work on a mosaic cube, the photometric
information for each input file is eliminated from the mosaic output
file.
Example:
Run **phocube** on a fly-by Cassini ISS-Wide Angle Camera image of
Enceladus. In this example, **phocube** will generate a 6-band output
cube.
!!! Note "The image used in this example has been processed through Level1 \[ingestion, spiceinit and radiometric calibration\]. Refer to: [Working with Cassini ISS Data](Working_with_Cassini_ISS_Data)"
Each band will contain the information asked for (parameters set to
true) in the following command:
phocube from=W1487302209_2.lev1.cub to=W1487302209_2_pho.cub
phase=true emission=true incidence=true latitude=true longitude=true
- All bands of the phocube output can be displayed in qview
- To access a selected band in an application, use the cube-attribute
syntax.
For example, calculate and report the average values of the Incidence
Angle (Band 3).
The command line for the **stats** applications is as follows:
stats from=W1487302209_2_pho.cub+3 to=W1487302209_2_inc_stats.pvl
The Example ISS Wide-Angle Camera image of Enceladus and the output of
**phocube** :
<figure class="inline" markdown>
![Cassini ISS WA-camera Enceladus](/assets/camera_geometry/Iss_WAC_enceladus_sm2.png){: style="width:225px;height:225px"}
<figcaption>Enceladus</figcaption>
</figure>
<figure class="inline" markdown>
![Iss\_WAC\_ema\_figure](/assets/camera_geometry/Iss_WAC_ema_figure.png "Phocube-Emission Angle Band"){: style="width:225px;height:225px"}
<figcaption>Phocube: Emission Angle Band</figcaption>
</figure>
<figure markdown>
![Iss\_WAC\_inc\_figure](/assets/camera_geometry/Iss_WAC_inc_figure.png "Phocube Incidence Angle Band"){: style="width:225px;height:225px"}
<figcaption>Phocube: Incidence Angle Band</figcaption>
</figure>
<figure class="inline" markdown>
![Iss\_WAC\_phase\_figure](/assets/camera_geometry/Iss_WAC_phase_figure.png "Phocube-Phase Angle Band"){: style="width:225px;height:225px"}
<figcaption>Phocube: Phase Angle Band</figcaption>
</figure>
<figure class="inline" markdown>
![Iss\_WAC\_lat\_figure](/assets/camera_geometry/Iss_WAC_lat_figure.png "Phocube-Latitude Band"){: style="width:225px;height:225px"}
<figcaption>Phocube: Latitude Band</figcaption>
</figure>
<figure markdown>
![Iss\_WAC\_lon\_figure](/assets/camera_geometry/Iss_WAC_lon_figure.png "Phocube-Longitude Band"){: style="width:225px;height:225px"}
<figcaption>Phocube: Longitude Band</figcaption>
</figure>
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# Learning About Map Projections
## What is a Map?
-----
A map is a two dimensional representation of a three dimensional object
such as a sphere, ellipsoid (egg-shape), or an irregular shaped body.
For planetary maps, these 3-D objects are the planets, their moons, and
irregular bodies such as asteroids. Maps allow scientists and
researchers to analyze and measure characteristics of features on the
body such as area, distance, and direction. See [Map
(Wikipedia)](http://en.wikipedia.org/wiki/Map) for a detailed
description of maps.
<figure markdown>
![MOLA](/assets/map_projections/Mola_of_sheet2a_thumb.jpeg "Example of a map made using data from the Mars Orbiter Laser Altimeter (MOLA)"){ width="100%" }
</figure>
## What is a Map Projection?
-----
A projection is an algorithm or equation for mapping a three dimensional
body onto a two dimensional surface such as paper, a computer screen, or
in our case, a digital image. There are many different types of
projections.
<figure markdown>
![Mercator Projection: The classic Mercator projection places a cylinder (rolled piece of paper) tangent to the equator.](/assets/map_projections/Mercator.gif){width="100%"}
<figcaption> Mercator Projection: The classic Mercator projection places a cylinder (rolled piece of paper) tangent to the equator. </figcaption>
</figure>
For additional information on types and properties of map projections
see [Map Projection
(USGS)](http://egsc.usgs.gov/isb//pubs/MapProjections/projections.html)
.
## ISIS3 Supported Projections
-----
**ISIS3 currently supports the following projections:**
- Equirectangular
- Lambert Azimuthal Equal Area
- Lambert Conformal
- Lunar Azimuthal Equal Area
- Mercator
- Mollweide
- Oblique Cylindrical
- Orthographic
- Planar
- Point Perspective
- Polar Stereographic
- Ring Cylindrical
- Robinson
- Simple Cylindrical
- Sinusoidal
- Transverse Mercator
- Upturned Ellipsoid Transverse Azimuthal
**Related Resources**
- [USGS: Map
Projections](http://egsc.usgs.gov/isb//pubs/MapProjections/projections.html)
- descriptions and comparisons of several map projections
## What is a Planetary Image Map?
-----
A primary capability of ISIS3 is to create map projected images of raw
instrument data. This allows researchers to make fundamental
measurements on and observations about the images.
The following is an example of a single Mars Global Surveyor (MGS) Mars
Orbital Camera (MOC) instrument image that has been transformed to a
planetary image map using the Sinusoidal projection.
| ![MOC image before transformation](/assets/map_projections/MOC1.jpeg){: style="width:300px;height:300px"} | ![MOC image after sinusoidal transformation](/assets/map_projections/SinuMOC1.jpeg){: style="width:300px;height:300px"} |
| --------------------------------------------------------------------- | ----------------------------------------------------------------------------------- |
| MOC image before transformation | MOC image after sinusoidal transformation |
## What is a Planetary Image Mosaic?
-----
Equally as important, ISIS3 allows a collection of raw instrument images
to be projected and stitched together (mosaicked) into large regional or
global maps.
<figure markdown>
![Sample\_mosaic\_themis.jpeg](/assets/map_projections/Sample_mosaic_themis.jpeg "Five Mars Odyssey THEMIS instrument images that have been projected and mosaicked to generate a regional planetary image map using the Sinusoidal projection"){: style="width:100%"}
<figcaption> Five Mars Odyssey THEMIS instrument images that have been projected and mosaicked to generate\n a regional planetary image map using the Sinusoidal projection </figcaption>
</figure>
## Defining a Map in ISIS3
-----
In order to project an image, characteristics of the map must be
established. They include the latitude/longitude coverage or ground
range, the pixel resolution, the target body radii, latitude and
longitude definitions, and the projection. In ISIS3 we record all of
this information in a Parameter Value Language (PVL) formatted map file.
For example this MGS MOC image was projected using the following:
```
Group = Mapping
TargetName = Mars
EquatorialRadius = 3396190.0 <meters>
PolarRadius = 3376200.0 <meters>
LatitudeType = Planetocentric
LongitudeDirection = PositiveEast
LongitudeDomain = 360
ProjectionName = Sinusoidal
CenterLongitude = 227.95679808356
MinimumLatitude = 10.766902750622
MaximumLatitude = 34.44419678224
MinimumLongitude = 219.7240455337
MaximumLongitude = 236.18955063342
PixelResolution = 426.87763879023 <meters/pixel>
End_Group
```
<figure markdown>
![SinuMOC1](/assets/map_projections/SinuMOC1.jpeg){: style="width:100%"}
<figcaption> Image projected using the above mapfile </figcaption>
</figure>
## Target Shape Definition
-----
The target shape must be defined in order to project an image. The shape
is characterized by the equatorial and polar radii of the body.
Depending on the projection, one or both of these values will be used.
The chart below shows which projections are for a sphere only (use only
the equatorial radius) and which work for ellipsoids:
Marked below are the PVL keywords used to define the target radii, which
must be given in units of meters.
```
Group = Mapping
TargetName = Mars
**EquatorialRadius = 3396190.0 <meters>**
**PolarRadius = 3376200.0 <meters>**
LatitudeType = Planetocentric
LongitudeDirection = PositiveEast
LongitudeDomain = 360
ProjectionName = Sinusoidal
CenterLongitude = 227.95679808356
MinimumLatitude = 10.766902750622
MaximumLatitude = 34.44419678224
MinimumLongitude = 219.7240455337
MaximumLongitude = 236.18955063342
PixelResolution = 426.87763879023 <meters/pixel>
End_Group
```
| Projection | Sphere | Ellipsoid |
| ------------------- | ------ | --------- |
| Sinusoidal | X | |
| Simple Cylindrical | X | |
| Equirectangular | X | |
| Polar Stereographic | X | X |
| Orthographic | X | |
| Mercator | X | X |
| Transverse Mercator | X | X |
| Lambert Conformal | X | X |
### Interactive Planetary Radii Demonstration
## Latitude Type
-----
Latitudes can be represented either in **planetocentric** or
**planetographic** form. The planetocentric latitude is the angle
between the equatorial plane and a line from the center of the body. The
**planetographic latitude** is the angle between the equatorial plane
and a line that is normal to the body. In a quick summary, both
latitudes are equivalent on a sphere (i.e., equatorial radius equal to
polar radius); however, they differ on an ellipsoid (e.g., Mars, Earth).
```
Group = Mapping
TargetName = Mars
EquatorialRadius = 3396190.0 <meters>
PolarRadius = 3376200.0 <meters>
**LatitudeType = Planetocentric**
LongitudeDirection = PositiveEast
LongitudeDomain = 360
ProjectionName = Sinusoidal
CenterLongitude = 227.95679808356
MinimumLatitude = 10.766902750622
MaximumLatitude = 34.44419678224
MinimumLongitude = 219.7240455337
MaximumLongitude = 236.18955063342
PixelResolution = 426.87763879023 <meters/pixel>
End_Group
```
### Quick Tips
- The latitude type will affect how other PVL keywords such as
MinimumLatitude, CenterLatitude are interpreted.
- Projections such as Sinusoidal, Simple Cylindrical, and
Equirectangular will place pixels differently in the image depending
on the latitude type. Pixel placement for other projections is not
affected. The LatitudeType keyword must be either **Planetocentric**
or **Planetographic** .
### Interactive Planetocentric and Planetographic Demonstration
**PLACE INTERACTIVE DEMO HERE**
## Longitude Direction and Domain
-----
Two keywords indicate how longitude is defined on the target body and
must be specified. The LongitudeDirection keyword indicates whether
longitude increases to the east or west, that is, positive to the east
or positive to the west. The LongitudeDomain keyword specifies how
longitudes should be interpreted 0° to 360° or -180° to 180°. In both
cases, these specifications affect other keywords and the interpretation
of other keywords, such as MinimumLongitude and CenterLongitude.
The LongitudeDirection keyword must be either PositiveEast or
PositiveWest, while the LongitudeDomain keyword must be 180 or 360.
These keywords are marked in the example below.
```
Group = Mapping
TargetName = Mars
EquatorialRadius = 3396190.0 <meters>
PolarRadius = 3376200.0 <meters>
LatitudeType = Planetocentric
**LongitudeDirection = PositiveEast**
**LongitudeDomain = 360**
ProjectionName = Sinusoidal
CenterLongitude = 227.95679808356
MinimumLatitude = 10.766902750622
MaximumLatitude = 34.44419678224
MinimumLongitude = 219.7240455337
MaximumLongitude = 236.18955063342
PixelResolution = 426.87763879023 <meters/pixel>
End_Group
```
### Interactive Longitude Direction of Domain Demonstration
**PLACE INTERACTIVE DEMO HERE**
## Ground Range
-----
The ground range defines the extent of the map. That is, the minimum and
maximum latitude/longitude values. Recall that these are in terms of the
latitude system, longitude direction, and longitude domain. In the
keywords below, the keywords marked define the ground range of the map.
```
Group = Mapping
TargetName = Mars
EquatorialRadius = 3396190.0 <meters>
PolarRadius = 3376200.0 <meters>
LatitudeType = Planetocentric
LongitudeDirection = PositiveEast
LongitudeDomain = 360
ProjectionName = Sinusoidal
CenterLongitude = 227.95679808356
**MinimumLatitude = 10.766902750622**
**MaximumLatitude = 34.44419678224**
**MinimumLongitude = 219.7240455337**
**MaximumLongitude = 236.18955063342**
PixelResolution = 426.87763879023 <meters/pixel>
End_Group
```
### Interactive Ground range demonstration
**PLACE INTERACTIVE DEMO HERE**
## Pixel Resolution
-----
The pixel resolution defines the size of pixels in a map projected image
in either meters per pixel, or pixels per degree. In the example below
is the marked keyword used to define the pixel resolution in meters per
pixel.
```
Group = Mapping
TargetName = Mars
EquatorialRadius = 3396190.0 <meters>
PolarRadius = 3376200.0 <meters>
LatitudeType = Planetocentric
LongitudeDirection = PositiveEast
LongitudeDomain = 360
ProjectionName = Sinusoidal
CenterLongitude = 227.95679808356
MinimumLatitude = 10.766902750622
MaximumLatitude = 34.44419678224
MinimumLongitude = 219.7240455337
MaximumLongitude = 236.18955063342
**PixelResolution = 426.87763879023 <meters/pixel>**
End_Group
```
Alternatively, the resolution can be defined as pixels per degree. For
example
```
Group = Mapping
TargetName = Mars
EquatorialRadius = 3396190.0 <meters>
PolarRadius = 3376200.0 <meters>
LatitudeType = Planetocentric
LongitudeDirection = PositiveEast
LongitudeDomain = 360
ProjectionName = Sinusoidal
CenterLongitude = 227.95679808356
MinimumLatitude = 10.766902750622
MaximumLatitude = 34.44419678224
MinimumLongitude = 219.7240455337
MaximumLongitude = 236.18955063342
**Scale = 138.85641255722 <pixels/degree>**
End_Group
```
### Interactive Exle of pixel resolutions
**PLACE INTERACTIVE DEMONSTRATION HERE**
## Projection and Parameters
-----
The final information required in the map file is the projection for
mapping the body to a two dimensional surface. In addition to the
projection name, projection-specific parameters must be provided. For
example, Sinusoidal requires the CenterLongitude. The following table
outlines the keywords required for each projection:
| ProjectionName | CenterLongitude | CenterLatitude | FirstStandardParallel | SecondStandardParallel | ScaleFactor | CenterAzimuth | Distance | CenterRadius |
| ------------------------------------ | --------------- | -------------- | --------------------- | ---------------------- | ----------- | ------------- | -------- | ------------ |
| Equirectangular | X | X | | | | | | |
| LambertAzimuthalEqualArea | X | X | | | | | | |
| LambertConformal | X | X | X | X | | | | |
| LunarAzimuthalEqualArea | | | | | | | | |
| Mercator | X | X | | | | | | |
| Mollweide | X | | | | | | | |
| ObliqueCylindrical | X | | | | | | | |
| Orthographic | X | X | | | | | | |
| Planar | | | | | | X | | |
| PointPerspective | X | X | | | | | X | |
| PolarStereographic | X | X | | | | | | |
| RingCylindrical | | | | | | X | | X |
| Robinson | X | | | | | | | |
| SimpleCylindrical | X | | | | | | | |
| Sinusoidal | X | | | | | | | |
| TransverseMercator | X | X | | | X | | | |
| UpturnedEllipsoidTransverseAzimuthal | X | | | | | | | |
## Projecting a Camera Cube
-----
To project a raw instrument (camera) cube to a map projected image you
must use the ISIS3 program
[**cam2map**](http://isis.astrogeology.usgs.gov/Application/presentation/Tabbed/cam2map/cam2map.html)
. The program allows you to enter a map file to specify the projection,
ground range, resolution, and target definition. If a map file is not
supplied the program will provide the following defaults:
| Parameters | Default Value |
| ------------------------------------------------------------------------------ | ----------------------------------------------------------------- |
| MinimumLatitude, MaximumLatitude, MinimumLongitude, MaximumLongitude | Automatically computed using information from the camera model |
| PixelResolution | Automatically computed using information from the camera model |
| EquatorialRadius, PolarRadius, LatitudeSystem, LongitudeRange, LongitudeDomain | Automatically computed using the TargetName from the cube labels. |
| CenterLatitude, CenterLongitude, and other projection specific parameters | Automatically computed using the middle of the ground range |
<figure markdown>
![Cam2map\_screenshot.jpeg](/assets/map_projections/Cam2map_screenshot.jpeg "Screenshot of the cam2map application"){: style="width:400px"}
<figcaption>A screenshot of the cam2map application</figcaption>
</figure>
### Quick Tips
- [**cam2map**](http://isis.astrogeology.usgs.gov/Application/presentation/Tabbed/cam2map/cam2map.html)
requires the input to be a camera cube and therefore ISIS3 must
support the camera model in order for this program to be successful.
- [**spiceinit**](http://isis.astrogeology.usgs.gov/Application/presentation/Tabbed/spiceinit/spiceinit.html)
must be run on the input cube as well.
## Problems at the Longitude Seams
-----
Problems can occur when working on images that cross the longitude seam.
For example, choosing a map file with:
```
LongitudeDomain = 360
```
A map file combined with an image that was viewed over the 0°/360° seam
will visually look like the following example.
When a camera acquires image data it is stored in a certain domain:
<figure markdown>
![Mars\_sphere\_illustration.png](/assets/map_projections/Mars_sphere_illustration.png "Thumbnail"){: style="width:400px"}
<figcaption>An illustration of the martian sphere at the 0-360 boundary</figcaption>
</figure>
When an image is created from the acquired data using the same domain,
the correct image is generated:
<figure markdown>
![180\_domain\_correct.png](/assets/map_projections/180_domain_correct.png "Thumbnail"){: style="width:400px"}
<figcaption>An image acquisition at the boundary using the same domain </figcaption>
</figure>
When an image is created in a different longitude domain, the resulting
image is incorrect (below, this image was scaled down to fit on the
screen):
<figure markdown>
![360\_domain\_incorrect.png](/assets/map_projections/360_domain_incorrect.png "Thumbnail"){: style="width:400px"}
<figcaption>An image acquisition at the boundary using a different domain </figcaption>
</figure>
These illustrate the problems that can arise when working with images
that cross the longitude seam.
The
[**cam2map**](http://isis.astrogeology.usgs.gov/Application/presentation/Tabbed/cam2map/cam2map.html)
program has an option which automatically changes the longitude domain
if it detects the image crossing the seam. If you turn this option off,
be aware you can generate large images with mostly NULL data. Note that
a similar problem occurs at the -180°/180° longitude boundary if
LongitudeDomain = 180.
## Power Tip: Reprojecting an Image Map
-----
Occasionally the need arises to reproject an image map. For example,
converting from a Simple Cylindrical to Sinusoidal projection:
![SimpleCylindrical.png](/assets/map_projections/SimpleCylindrical.jpeg "Thumbnail"){: style="width:40%"}
![Blue\_right\_arrow.gif](/assets/map_projections/Blue_right_arrow.gif "Thumbnail"){: style="width:10%"}
![SinusodialProjection.jpeg](/assets/map_projections/SinusodialProjection.jpeg "Thumbnail"){: style="width:40%"}
Another purpose for reprojecting an image map is to get all the images
with the same projection, parameters, resolution, latitude system, etc
in order to mosaic. For example,
<figure class="inline" markdown>
![Simple\_135-110.png](/assets/map_projections/Simple_135-110.jpeg "Simple Cylindrical"){: style="width:250px;height:150px"}
<figcaption>Simple Cylindrical</figcaption>
</figure>
<figure class="inline" markdown>
![Sinusodial\_135-110.png](/assets/map_projections/Sinusodial_135-110.jpeg "Sinusoidal"){: style="width:250px;height:150px"}
<figcaption>Sinusoidal</figcaption>
</figure>
<figure markdown>
![Mosaic\_sinus.png](/assets/map_projections/Mosaic_sinus.jpeg "Sinusoidal Mosaic from Mars"){: style="width:250px;height:150px"}
<figcaption>Sinusoidal Martian Mosaic</figcaption>
</figure>
-----
The program for reprojecting an image map is
[**map2map**](https://isis.astrogeology.usgs.gov/Application/presentation/Tabbed/map2map/map2map.html)
.
## Power Tip: Making Mosaics
-----
In order to mosaic a set of cubes they must all be projected in
[**cam2map**](http://isis.astrogeology.usgs.gov/Application/presentation/Tabbed/cam2map/cam2map.html)
or
[**map2map**](http://isis.astrogeology.usgs.gov/Application/presentation/Tabbed/map2map/map2map.html)
using the SAME pixel resolution, target definition, and projection and
parameters (e.g., center longitude, etc). Note the ground range does not
need to be the same. This is fairly straight-forward as you can project
all the images with the same map file, just leave out the
MinimumLatitude, MinimumLongitude, MaximumLatitude, MaximumLongitude
parameters.
In the example below, we see the mapping file used to project the five
images in the THEMIS mosaic below
```
Group = Mapping
LatitudeType = Planetocentric
LongitudeDirection = PositiveEast
LongitudeDomain = 360
ProjectionName = Sinusoidal
CenterLongitude = 354.0
PixelResolution = 100.0 <meters/pixel>
End_Group
End
```
<figure markdown>
![Mosaic after](/assets/map_projections/Mosaic_after.jpeg){: style="width:250px"}
<figcaption>THEMIS Mosaic</figcaption>
</figure>
## Creating a mosaic
-----
- The most convenient way to mosaic a number of map projected images
is to use the
[**automos**](http://isis.astrogeology.usgs.gov/Application/presentation/Tabbed/automos/automos.html)
application. Automos reads a list of input images, computes the
latitude and longitude coverage of all the images and creates the
output mosaic.
- The
[**mapmos**](http://isis.astrogeology.usgs.gov/Application/presentation/Tabbed/mapmos/mapmos.html)
application mosaics one image at a time. Remember to set create=true
the first time mapmos is run with the first image in order to create
the output mosaic file.
- It is possible to mosaic images together by specifying the output
pixel coordinate placement using the
[**handmos**](http://isis.astrogeology.usgs.gov/Application/presentation/Tabbed/handmos/handmos.html)
application. This would be for any ISIS3 image cubes that do not
have a camera model or cartographic mapping information that is
required by mapmos and automos.
## Other Hints and Tips
-----
- In lieu of using a standard text editor, the programs
[**maptemplate**](http://isis.astrogeology.usgs.gov/Application/presentation/Tabbed/maptemplate/maptemplate.html)
or
[**mosrange**](http://isis.astrogeology.usgs.gov/Application/presentation/Tabbed/mosrange/mosrange.html)
can be used to assist in the building of map files.
- A map projected image can be used as a map file. For example, a
Viking and MOC image taken of the same area can be projected by
running
[**cam2map**](http://isis.astrogeology.usgs.gov/Application/presentation/Tabbed/cam2map/cam2map.html)
on the Viking image using the defaults and then the MOC image
projected using the Viking image as the map file. The MOC image will
have the same projection, target definition, resolution, and ground
range so that the images can be easily compared.
- In general, the pixel resolution of the image map is only accurate
in certain portions of the image; however, this is entirely
dependent upon the projection you select. The labels of the output
cube will have a keyword called TrueScaleLatitude and/or
TrueScaleLongitude and these represent where the resolution is
accurate. The accuracy may be true along that meridian or parallel
or point. Again this depends upon the projection.
- The output map image size will vary depending on ground range and
pixel resolution. Care should be taken to ensure your output image
is not too large. You can check the size of image that will produced
with a fully-defined map file by using the
[**mapsize**](http://isis.astrogeology.usgs.gov/Application/presentation/Tabbed/mapsize/mapsize.html)
program.
</div>
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# Overview of Map Projecting Images
## Introduction
Converting a raw instrument/camera cube (Level1) to a map projected
image (Level2) is a fundamental capability of ISIS.
The default transformation is based on the original viewing geometry of
the observation, relative position of the target body and the definition
of the output map projection.
The main application to project an image is
[**cam2map**](http://isis.astrogeology.usgs.gov/Application/presentation/Tabbed/cam2map/cam2map.html)
.
```
cam2map from=camera_cube_level1.cub to=level2_cube.cub
```
## ISIS Requirements
-----
- The image data must be part of a mission instrument 'camera model'
that is supported within ISIS
- Proper ingestion of the image data into ISIS ( [**Importing Mission
Data**](Locating_and_Ingesting_Image_Data) )
- Available [**SPICE**](SPICE_Information) information for every
individual image
- A [**map template**](/concepts/Learning About Map Projections) to define an
output map projection
## Supported Map Projections
-----
[**ISIS Supported Projections**](/concepts/Learning About Map Projections)
- For detailed information about Map Projections within ISIS refer to
[Learning About Map Projections](/concepts/Learning About Map Projections) .
## Defining an Output Map
-----
### ISIS Defaults
ISIS supplies 'basic' map templates that set the ProjectionName
parameter to a supported map projection.
- The map templates can be found in: $ISISDATA/base/templates/maps/
- These map templates can be selected through the MAP parameter in
'cam2map' (current default is sinusoidal).
- In conjunction with the supplied map templates; the default for an
output map are as follows:
- The original [**raw camera geometry**](/concepts/Camera Geometry)
- [**Computed parameters**](/concepts/Learning About Map Projections)
- The target body is defined in the system defaults which can be
found in $ISISDATA/base/templates/targets/.
### When to Generate A Custom Defined Map Template
- The viewing geometry of an image(s) are important details to
consider when defining an output map projection.
- There are a number of applications that report relevant
[**camera geometry**](/concepts/Camera Geometry) information for a given
image or a list of images.
- Does your input cover the north or south pole of the body?
- Do you want your output map to be centered at a specific
latitude/longitude?
- Do you plan on mosaicking your images together?
- An output mosaic (digital image map-DIM) is a major
consideration before projecting multiple images. Refer to
[**Making Mosaics**](/concepts/Learning About Map Projections).
#### The Custom Map Template
In order to project an image to a specific map projection, you'll need
to set up a list of parameters based on the projection you wish to use.
Use the
[**maptemplate**](https://isis.astrogeology.usgs.gov/Application/presentation/Tabbed/maptemplate/maptemplate.html)
application program (or your favorite text editor) to set up a **map
template** file defining the mapping parameters for the projection. The
following is a an example of a map template file for defining the
projection of an image of Mars to the sinusoidal projection:
```
Group = Mapping
TargetName = Mars
EquatorialRadius = 3396190.0 <meters>
PolarRadius = 3376200.0 <meters>
LatitudeType = Planetocentric
LongitudeDirection = PositiveEast
LongitudeDomain = 360
ProjectionName = Sinusoidal
CenterLongitude = 227.95679808356
MinimumLatitude = 10.766902750622
MaximumLatitude = 34.44419678224
MinimumLongitude = 219.7240455337
MaximumLongitude = 236.18955063342
PixelResolution = 426.87763879023 <meters/pixel>
End_Group
```
!!! Note "A separate map or map-projected image can be used as a map template file in cam2map. These files are required to have the ISIS Mapping Group keyword labels."
## Camera Distortion Correction
-----
Within ISIS, the map projection software includes correcting modeled
camera distortions for each supported instrument. When map projecting an
image, the camera distortion correction and geometric transformation are
performed simultaneously so that resampling is performed only once and
pixel resolution loss is minimal.
## Projecting the Image
-----
The
[**cam2map**](https://isis.astrogeology.usgs.gov/Application/presentation/Tabbed/cam2map/cam2map.html)
application converts a camera (instrument) image to a map projected
image. cam2map will automatically compute defaults for most of the
mapping parameters, so you only need to define a subset of the
parameters in your map template (e.g. ProjectionName).
- If you are projecting several images with the same projection
parameters, **you can apply the same map template** for all of your
images simply by removing the latitude longitude range parameters
(MinimumLatitude, MaximumLatitude, MinimumLongitude, and
MaximumLongitude) from your map template.
- **cam2map will automatically calculate parameter values for you** --
all you *really* need is the projection name in your map template.
- If you are planning on mosaicking your projected images, make sure
the **PixelResolution** , **CenterLongitude** and **CenterLatitude**
is the **same** for all images.
## Related ISIS Applications
-----
See the following ISIS documentation for information about the
applications you will need to use to perform this procedure:
- [**maptemplate**](https://isis.astrogeology.usgs.gov/Application/presentation/Tabbed/maptemplate/maptemplate.html)
: set up a map projection parameter template for map projecting
cubes
- [**cam2map**](https://isis.astrogeology.usgs.gov/Application/presentation/Tabbed/cam2map/cam2map.html)
: project a cube to a map projection
mkdocs.yml
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...@@ -42,6 +42,8 @@ nav: ...@@ -42,6 +42,8 @@ nav:
- Generating an ISD, creating a CSM model, and converting coordinates: getting-started/CSM Stack/ImageToGroundTutorial.ipynb - Generating an ISD, creating a CSM model, and converting coordinates: getting-started/CSM Stack/ImageToGroundTutorial.ipynb
- How-To Guides: - How-To Guides:
- Home: how-to-guides/index.md - Home: how-to-guides/index.md
- Image Processing:
- Map Projecting Images: how-to-guides/Image Processing/Map Projecting Images.md
- Software Management: - Software Management:
- ISIS Public Release Process: how-to-guides/Software Management/Public Release Process.md - ISIS Public Release Process: how-to-guides/Software Management/Public Release Process.md
- Software Support: how-to-guides/Software Management/Software Support.md - Software Support: how-to-guides/Software Management/Software Support.md
...@@ -49,7 +51,11 @@ nav: ...@@ -49,7 +51,11 @@ nav:
- How To Write ISIS Tests with CTest and GTest: "how-to-guides/ISIS Developer Guides/Writing ISIS Tests with CTest and GTest.md" - How To Write ISIS Tests with CTest and GTest: "how-to-guides/ISIS Developer Guides/Writing ISIS Tests with CTest and GTest.md"
- App Testing CookBook: "how-to-guides/ISIS Developer Guides/App Testing Cookbook.md" - App Testing CookBook: "how-to-guides/ISIS Developer Guides/App Testing Cookbook.md"
- Class Requirements For Using Doxygen Tags: "how-to-guides/ISIS Developer Guides/Class Requirements For Using Doxygen Tags.md" - Class Requirements For Using Doxygen Tags: "how-to-guides/ISIS Developer Guides/Class Requirements For Using Doxygen Tags.md"
- Concepts: concepts/index.md - Concepts:
- Home: concepts/index.md
- Camera Geometry and Projections:
- Camera Geometry: concepts/Camera Geometry.md
- Learning About Map Projections: concepts/Learning About Map Projections.md
- Manuals: manuals/index.md - Manuals: manuals/index.md
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