Merge branch 'indexes' into 'main'

### Adding your files

> See [mkdocs material docs](https://squidfunk.github.io/mkdocs-material/getting-started/) for information on how to work with mkdoc's material theme and it's features. 

1. Determine what category your docs belong to by reading [the summary on the README](#understanding-the-doc-system). 

2. Write your either in Markdown or as a Jupyter notebook and add it under the directory for that category. 

3. Update `mkdocs.yml`, add a new file somewhere appropriate under `nav:` 

1. Include minimum explanation; the focus is on "learning by doing"

1. Focus on the steps required to complete the goal. 

Concrete things your tutorial needs: 

- If your tutorial requires installing software, list what software and their versions and clear instructions on how to install them. Feel free to point to other points of the doc that already have boilerplate info like "Go here to read on how to set up a custom ISISPreferences file". 

- If your tutorial has data, use generative data or data that is in the repo. Avoid external data dependencies. Before data is committed into the repo, check if [existing data can be re-used](./data/). If new data needs to be committed, make sure it is small so as not to increase the data burden.   

- Make sure to make the lesson clear in the title. Also, make it clear in the tutorial with something like "Lessons learned in this tutorial:". 

Examples: 

* Getting Started: ISIS image ingestion to map projected image, ingesting, bundling, and projecting an image list 

* Getting Started: generating an ISD and CSM camera model

* Getting Started: Generating an ISD and CSM camera model

* Getting Started: Generate a control network with an image matcher 

### How-to Guides 

1. Solve practical problems for more experienced users

1. Offer more ambiguous starting points; they should be re-usable in many different contexts 

1. Provide little explanation, mostly showing steps on how to accomplish the task

1. Are generally much shorter than getting started docs

1. Can be much shorter than getting started docs

Examples: 

* How-to: generate an ISD via loads with specific kernels

* How-to: get GEOJSON from ISIS footprints

* How-to: Generate an ISD via loads with specific kernels

* How-to: Get GEOJSON from ISIS footprints

### Concepts 

Software manuals centered on the code of the library. These are generally links to the library's programmatically generated API docs. Think Sphinx docs and/or Doxygen-generated docs. 

Examples: 

* Programatically generated Python/C++ API docs from inline doc strings

* Programatically Generated Python/C++ API docs from inline doc strings

* RESTful API docs from an OpenAPI spec file 

*[Adjusted]: The term, Adjusted, refers to the output pixel coordinate or output geographic location within a control network. Applications such as pointreg or jigsaw report and update the "Adjusted" output pixel coordinate (pointreg) or geographic location (jigsaw) in the output control network. 

*[Band]: A 3rd dimensional layer of pixels in an image, typically representing spectral information. The number of bands indicates the depth of an image in terms of these layers. 

*[Bit]: Short for binary digit, which in a computer is the smallest unit of storage. Bits are either "0" or "1". 

*[Byte]: Short for binary term. A byte is a collection of computer bits. On most modern computers, a byte is a group of eight bits. Typically, computers handle and store information in binary (base-2), and a group of eight bits represents an eight digit binary number.

*[CSM]: Community Sensor Model. A standard for sensor models USGS uses for interoperability. 

*[SPICE]: Spacecraft & Planetary ephemerides, Instrument C-matrix and Event kernels. SPICE refers to all the information required by ISIS in order to compute and map each image pixel onto a surface with reference to spacecraft position, sun position, instrument, and mission activities. ISIS uses software (ToolKit) supplied by the Navigation and Ancillary Information Facility (NAIF) for SPICE access and kernel management (Refer to spiceinit). 

*[NAIF]: Navigation and Ancillary Information Facility. They engineered and support the SPICE observation geometry information system. 

*[NULL]: NULL is a Special Pixel value that is tracked and reported to the user. NULL represents "No Data". NULL is set in all 8, 16, 32-bit type image data. 

*[LRS]: LRS [Low Representation Saturation] is a representation special pixel value that is tracked and reported to the user. LRS is set when an ISIS application causes the output DN pixel to fall 'below' the possible range of valid values. 

*[HRS]: HRS [High Representation Saturation] is a representation special pixel value that is tracked and reported to the user. HRS is set when an ISIS application causes the output DN pixel to fall 'above' the possible range of valid values. 

*[LIS]: LIS [Low Instrument Saturation] is an instrument special pixel value that is tracked and reported to the user. LIS is set during the ingestion of the image data into ISIS. The input image sensor acquired a value too low to be measured accurately. 

*[HIS]: HIS [High Instrument Saturation] is an instrument special pixel value that is tracked and reported to the user. HIS is set during the ingestion of the image data into ISIS. The input image sensor acquired a value too high to be measured accurately. 

*[Cube]: A cube is a 3-dimensional image with axis: samples, lines, and bands. The physical dimensions of a cube are called the number of samples (NS), number of lines (NL), and number of bands (NB). 

*[Line]: A row of pixels in an image, typically representing spatial information. The number of lines indicates the total height of an image in pixels. 

*[Sample]: A column of pixels in an image, typically representing spatial information. The number of samples indicates the total width of an image in pixels. 

*[Level0]: Level0 is a standard cartographic processing phase that describes an image has been ingested into ISIS (PDS EDR) and will often have SPICE information loaded on the ISIS cube labels (spiceinit). Level0 image cubes are often the input to mission specific radiometric calibration applications if supported in ISIS. 

*[Level1]: Level1 is a standard cartographic processing phase that describes an image has been radiometrically calibrated (PDS CDR or the ISIS output of a mission specific calibration application) with SPICE information loaded on the ISIS cube labels. 

*[Level2]: Level2 is a standard cartographic processing phase that describes an image has been map projected (PDS RDR). The Level2 image cube labels contain Mapping keywords that describe the projection and all associated map characteristics. 

*[Elevation]: The height above or below a fixed point on the surface of a body. 

*[Albedo]: Reflectivity of a surface or particle. Commonly in I/F units for radiometrically calibrated data. 

*[Emissivity]: A measure describing a substance's ability to absorb and radiate electromagnetic energy. 

*[Radiance]: A measurement describing the amount of electromagnetic energy emitted from an area of a planet. 

*[Reflectance]: The ratio of reflected energy to incoming energy. 

*[Radius]: The distance (vector) value between the center of and a point on a circle, sphere, ellipse or ellipsoid. Refer to qview, camstats, or campt as examples of applications that report radius value at every image pixel location. 

*[I/F]: Irradiance/SolarFlux. Unit of DN values for a reference distance of target body from the Sun (5.2 AU). The valid values range between 0.0 and 1.0. 

*[Azimuth]: A clockwise angle from a point of origin to a point of interest. 

*[Declination]: Declination (Dec) is one of two angles of the North Pole of a target body as a function of time. 

*[Latitude]: Latitude represents a geographic position and is measured from the equator, with positive longitudes going North and negative values going South. 

*[Longitude]: Longitude represents a geographic position and is measured from a specified Prime Meridian (default is IAU) for the target body. 

*[UTC]: Coordinated Universal Time (UTC) is a system of time keeping that gives an understandable name to each instant of time. The names are formed from the calendar date and time of day. UTC format consists of year, month, day, hour, minutes and seconds. 

*[PVL]: Parameter Value Language (PVL) is used extensively by ISIS as a standard keyword value type language for naming and expressing data values. PVL format in ISIS is compatible with syntax used by the Planetary Data System. 

*[MAP]: A representation of a three dimensional target such as a sphere, ellipsoid or an irregular shaped body onto a plane 

*[IAU]: The International Astronomical Union 

*[Scale]: The map resolution measured in pixels per degree 

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!!! 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\]

      - **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](../Camera%20Geometry%20and%20Projections/Learning%20About%20Map%20Projections.md)

# Concepts

Concept docs are understanding-oriented docs. The focus is on explaining a topic. These expand the user's understanding of a topic without elaborating on particulars of code while providing context or descriptions. Information from concept docs might be among other docs, but getting started docs, how-to guides, or software manuals can reference concept docs that go in-depth on the topic. 

## For Readers 

[comment]: <> (This is a good place to mention any places for someone to start looking in. Highlight specific docs with high value or we identify readers commonly want to see)

Use the table of contents on the left to browse docs covering different concepts. 

Good place to start is with the [glossary](glossary/glossary.md)

## For Authors 

These docs are predominately abstracts on a particular topic. 

Good concept docs have: 

1. A clear and specific topic of discussion   

1. Little to no instruction 

1. Context or descriptions of: 

    * Historical background of the software and/or why it exists

    * Engineering of a software tool or component thereof 

    * Concepts commonly found across software 

??? Info "Examples"

    * Dictionaries or Glossary of terms

    * Explanation of what control networks are and why we use them

    * History and explanation of ALE's architecture 

    * Differences between CSM and ISIS camera models 

See the [git repo](https://code.usgs.gov/astrogeology/asc-public-docs) for more in-depth info on how to contribute new docs. 

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