About

georef-lrpt application can georeference images acquired via LRPT protocol. The result will be a .png file and a .vrt file. VRT file can be used by gdal to create GeoTIFF.

Features

• Supported satellites: METEOR-M 2 (NORAD ID: 40069), METEOR-M 2-2 (NORAD ID: 44387)
• 3 channels + 1 alpha channel
• Alpha channel is generated for those regions where was no packets received for all 3 other channels
• Detect extents for manual split on anti-meridian

How to use

Step 1. Obtain LRPT binary files

These files should contain VCDU (data link layer frame) as they were received from the satellite. Find examples of such files in the src/test/resources/ directory.

Note: VCDU frames can carry variable number of image packets. So better to have a single binary file with all VCDU sorted in the ascending order or several files with filenames in the ascending order.

Step 2. Obtain TLE

TLE of the satellite. It should be in the 2-line or 3-line format.

Note: TLE should be generated for the same day as binary files for better alignment precision.

Step 3. Run

Get the help of all supported parameters using the command below:

java -jar georef-lrpt.jar --help

Example run:

java -jar georef-lrpt.jar --output-dir . --tle-file src/test/resources/2022-12-20.txt --vcdu-files "src/test/resources/*.vcdu"

The output will contain .png file and .vrt file.

Step 4. Convert .vrt into GeoTIFF using gdal

Use gdal to convert .vrt into GeoTIFF:

gdalwarp -tps -overwrite -of GTIFF 2022_12_20_20_25_30_134_-14_162_-8.vrt 2022_12_20_20_25_30.tiff

The command above will create GeoTIFF file in the EPSG:4326 projection ( longlat WGS84 ). This projection can be further converted into epsg:3857 to use from online maps like Google maps and OpenStreetMap.

Anti-meridian

GDAL and QGIS cannot detect if image is wrapped around projection. Thus special handling is needed.

1. Extract geodetic coordinates from the .vrt filename. georef-lrpt will generate .vrt filenames according to the format: <first .vcdu filename>_<minX>_<minY>_<maxX>_<maxY>.vrt. Please note that each coordinate can be negative. For example: 2022_12_20_20_25_30_134_-14_162_-8.vrt Has longitude from 134 to 162 (west to east) and latitude from -14 to -8 (south to north).

2. Generate 2 separate tiff files from the same .vrt using gdalwrap. For the filename 2022_12_20_18_44_50_142_-55_-173_-11.vrt two commands need to be executed gdalwarp -tps -overwrite -te 142 -55 180 -11 -of GTiff 2022_12_20_18_44_50_142_-55_-173_-11.vrt 2022_12_20_18_44_50-left.tiff and gdalwarp -tps -overwrite -te -180 -55 -173 -11 -of GTiff 2022_12_20_18_44_50_142_-55_-173_-11.vrt 2022_12_20_18_44_50-right.tiff

Then left and right images can be added to the map. On the screenshot below the right image is drawn without alpha channel, just to highlight wrapped output.