bmi-topography 0.9.0
Fetch and cache land elevation data from OpenTopography
License: MIT License
Requires Python: >=3.10
Keywords: bmi, srtm, alos, nasadem, copernicus, topography, elevation, dem, data, csdms, usgs, gedi, gebco, mrdem

<!-- Links (by alpha) -->

[bmi]: https://bmi.csdms.io
[bmi-topo-examples]: https://github.com/csdms/bmi-topography/tree/main/examples
[bmi-topo-repo]: https://github.com/csdms/bmi-topography
[conda-env]: https://docs.conda.io/projects/conda/en/latest/user-guide/tasks/manage-environments.html
[ot]: https://opentopography.org/
[ot-api-key]: https://opentopography.org/blog/introducing-api-keys-access-opentopography-global-datasets
[ot-rest]: https://portal.opentopography.org/apidocs/
[rioxarray]: https://corteva.github.io/rioxarray/stable/getting_started/getting_started.html
[xarray]: https://docs.xarray.dev/en/stable/index.html
[xarray-da]: https://docs.xarray.dev/en/stable/generated/xarray.DataArray.html
[xarray-plot]: https://docs.xarray.dev/en/stable/generated/xarray.DataArray.plot.html

<!-- Links to datasets on OT -->
[SRTMGL3]: https://portal.opentopography.org/raster?opentopoID=OTSRTM.042013.4326.1
[SRTMGL1]: https://portal.opentopography.org/raster?opentopoID=OTSRTM.082015.4326.1
[SRTMGL1_E]: https://portal.opentopography.org/raster?opentopoID=OTSRTM.082016.4326.1
[AW3D30]: https://portal.opentopography.org/raster?opentopoID=OTALOS.112016.4326.2
[AW3D30_E]: https://portal.opentopography.org/raster?opentopoID=OTALOS.082017.4326.1
[SRTM15Plus]: https://portal.opentopography.org/datasetMetadata?otCollectionID=OT.122019.4326.1
[NASADEM]: https://doi.org/10.5069/G93T9FD9
[COP30]: https://portal.opentopography.org/raster?opentopoID=OTSDEM.032021.4326.3
[COP90]: https://portal.opentopography.org/raster?opentopoID=OTSDEM.032021.4326.1
[EU_DTM]: https://portal.opentopography.org/datasetMetadata?otCollectionID=OT.092022.3035.1
[GEDI_L3]: https://portal.opentopography.org/datasetMetadata?otCollectionID=OT.032022.4326.1
[GEBCOIceTopo]: https://portal.opentopography.org/raster?opentopoID=OTSDEM.122023.4326.1
[GEBCOSubIceTopo]: https://portal.opentopography.org/raster?opentopoID=OTSDEM.122023.4326.2
[CA_MRDEM_DSM]: https://doi.org/10.5069/G9N8780J
[CA_MRDEM_DTM]: https://doi.org/10.5069/G9N8780J
[USGS30m]: https://portal.opentopography.org/raster?opentopoID=OTNED.012021.4269.2
[USGS10m]: https://portal.opentopography.org/raster?opentopoID=OTNED.012021.4269.1
[USGS1m]: https://portal.opentopography.org/raster?opentopoID=OTNED.012021.4269.3

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# bmi-topography

*bmi-topography* is a Python library for fetching and caching
land elevation data
using the [OpenTopography][ot] [REST API][ot-rest].

The *bmi-topography* library provides access to the following global raster datasets:

* [SRTMGL3][SRTMGL3] (SRTM GL3 90m)
* [SRTMGL1][SRTMGL1] (SRTM GL1 30m)
* [SRTMGL1_E][SRTMGL1_E] (SRTM GL1 Ellipsoidal 30m)
* [AW3D30][AW3D30] (ALOS World 3D 30m)
* [AW3D30_E][AW3D30_E] (ALOS World 3D Ellipsoidal, 30m)
* [SRTM15Plus][SRTM15Plus] (Global Bathymetry SRTM15+ V2.1)
* [NASADEM][NASADEM] (NASADEM Global DEM)
* [COP30][COP30] (Copernicus Global DSM 30m)
* [COP90][COP90] (Copernicus Global DSM 90m)
* [EU_DTM][EU_DTM] (DTM 30m)
* [GEDI_L3][GEDI_L3] (DTM 1000m)
* [GEBCOIceTopo][GEBCOIceTopo] (Global Bathymetry 500m)
* [GEBCOSubIceTopo][GEBCOSubIceTopo] (Global Bathymetry 500m)
* [CA_MRDEM_DSM][CA_MRDEM_DSM] (DSM 30m)
* [CA_MRDEM_DTM][CA_MRDEM_DTM] (DTM 30m)

as well as these USGS 3DEP raster datasets:

* [USGS30m][USGS30m]
* [USGS10m][USGS10m]
* [USGS1m][USGS1m] (limited to academic users)

The library includes an API and a CLI that accept
the dataset type,
a latitude-longitude bounding box, and
the output file format.
Data are downloaded from OpenTopography and cached locally.
The cache is checked before downloading new data.
Data from a cached file can optionally be loaded into an
[xarray][xarray] [DataArray][xarray-da]
through [rioxarray][rioxarray].

The *bmi-topography* API is wrapped with a
[Basic Model Interface][bmi] (BMI),
which provides a standard set of functions for coupling with data or models
that also expose a BMI.
More information on the BMI can found in its [documentation][bmi].

## Installation

Install the latest stable release of *bmi-topography* with `pip`:
```
pip install bmi-topography
```
or with `conda`:
```
conda install -c conda-forge bmi-topography
```

The *bmi-topography* library can also be built and installed from source.
The library uses several other open source libraries,
so a convenient way of building and installing it is within a
[conda environment][conda-env].
After cloning or downloading the *bmi-topography*
[repository][bmi-topo-repo],
change into the repository directory
and set up a conda environment with the included environment file:
```
conda env create --file=environment.yml
```
Then build and install *bmi-topography* from source with
```
pip install -e .
```

## API key

To better understand usage,
OpenTopography [requires an API key][ot-api-key] to access datasets they host.
Getting an API key is easy, and it's free:
just follow the instructions in the link above.

Once you have an API key,
there are three ways to use it with *bmi-topography*:

1. *parameter*: Pass the API key as a string through the `api_key` parameter.
2. *environment variable*: In the shell, set the `OPENTOPOGRAPHY_API_KEY` environment variable to the API key value.
3. *dot file*: Put the API key in the file `.opentopography.txt` in the current directory or in your home directory.

If you attempt to use *bmi-topography* to access an OpenTopography dataset without an API key,
you'll get an error like this:
```
requests.exceptions.HTTPError: 401 Client Error: This dataset requires an API Key for access.
```

## Examples

A brief example of using the *bmi-topography* API is given in the following steps.

Start a Python session and import the `Topography` class:
```python
>>> from bmi_topography import Topography
```

For convenience,
a set of default parameter values for `Topography` are included in the class definition.
Copy these and modify them with custom values:
```python
>>> params = Topography.DEFAULT.copy()
>>> params["south"] = 39.93
>>> params["north"] = 40.00
>>> params["west"] = -105.33
>>> params["east"] = -105.26
>>> params
{'dem_type': 'SRTMGL3',
 'south': 39.93,
 'north': 40.0,
 'west': -105.33,
 'east': -105.26,
 'output_format': 'GTiff',
 'cache_dir': '~/.bmi_topography'}
```
These coordinate values represent an area around Boulder, Colorado.

Make an instance of `Topography` with these parameters:
```python
>>> boulder = Topography(**params)
```
Display the download URL:
```python
>>> boulder.url
https://portal.opentopography.org/API/globaldem?demtype=SRTMGL3&south=39.93&north=40.0&west=-105.33&east=-105.26&outputFormat=GTiff&API_Key=demoapikeyot2022
```
then fetch the data from OpenTopography:
```python
>>> boulder.fetch()
PosixPath('/Users/mpiper/.bmi_topography/SRTMGL3_39.93_-105.33_40.0_-105.26.tif')
```
This step might take a few moments,
and the time it takes will increase for requests of larger areas.
Note that the file has been saved to a local cache directory.

Load the data into an xarray `DataArray` for further work:
```python
>>> boulder.load()
<xarray.DataArray 'SRTMGL3' (band: 1, y: 84, x: 84)>
array([[[2052, 2035, ..., 1645, 1643],
        [2084, 2059, ..., 1643, 1642],
        ...,
        [2181, 2170, ..., 1764, 1763],
        [2184, 2179, ..., 1773, 1769]]], dtype=int16)
Coordinates:
  * band         (band) int64 1
  * x            (x) float64 -105.3 -105.3 -105.3 ... -105.3 -105.3 -105.3
  * y            (y) float64 40.0 40.0 40.0 40.0 ... 39.93 39.93 39.93 39.93
    spatial_ref  int64 0
Attributes:
    _FillValue:    0.0
    scale_factor:  1.0
    add_offset:    0.0
    units:         meters
    location:      node
```

Coordinate reference system (CRS) information is stored in the `spatial_ref` non-dimension coordinate:
```python
>>> boulder.da.spatial_ref
<xarray.DataArray 'spatial_ref' ()>
array(0)
Coordinates:
    spatial_ref  int64 0
Attributes:
    crs_wkt:                      GEOGCS["WGS 84",DATUM["WGS_1984",SPHEROID["...
    semi_major_axis:              6378137.0
    semi_minor_axis:              6356752.314245179
    inverse_flattening:           298.257223563
    reference_ellipsoid_name:     WGS 84
    longitude_of_prime_meridian:  0.0
    prime_meridian_name:          Greenwich
    geographic_crs_name:          WGS 84
    grid_mapping_name:            latitude_longitude
    spatial_ref:                  GEOGCS["WGS 84",DATUM["WGS_1984",SPHEROID["...
    GeoTransform:                 -105.33041666668363 0.000833333333333144 0....
```

Display the elevations with the default xarray `DataArray` [plot][xarray-plot] method.
```python
>>> import matplotlib.pyplot as plt
>>> boulder.da.plot()
>>> plt.show()
```

![Example elevation data displayed through *xarray*.](./examples/bmi-topography_ex.png)

For examples with more detail,
see the two Jupyter Notebooks,
Python script, and shell script
included in the [examples][bmi-topo-examples] directory
of the *bmi-topography* repository.

<!-- skip-docs-link -->

User and developer documentation for *bmi-topography*
is available at https://bmi-topography.csdms.io.

Credits
=======

Project lead
------------

* Mark Piper

Contributors
------------

* Eric Hutton
* Jeffrey Kwang
* Mark Piper

Acknowledgments
---------------

This work is supported by the National Science Foundation under Award No.
[2026951](https://www.nsf.gov/awardsearch/showAward?AWD_ID=2026951),
*EarthCube Capabilities: Cloud-Based Accessible and Reproducible Modeling for Water and Sediment Research*.

MIT License
===========

Copyright (c) 2021 Community Surface Dynamics Modeling System

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