QGIS MGRS Notes

Abstract

QGIS is a free geoinformation system. This document collects my usage notes for QGIS focusing on usage together with MGRS (Military Grid Reference System).

Useful Plugins

• MGRS Tools 3.0.1 - Allows pointing QGIS at a specific MGRS coordinate.

EPSG Codes to Use

Description	EPSG	Recommendation
WGS84 UTM 32n	32632	Use this by default
ETRS89 UTM 32n	25832	Possible source format; compatible for small scales
ED50 UTM 32n	23032	Do not use except for legacy applications
Gauß-Krüger Zone 2	31466	Do not use except for special applications
WGS84 world-wide	4326	Might sometimes make sense to use
Google Maps	3857	Use as “convert from” EPSG

Configuring an MGRS Grid

The following code can be used to create labels that indicate UTM coordinates (if one leaves out the brackets while reading) and MGRS coordinates (if one ignores the brackets while reading). This comes close to the typical notation of having the UTM parts in superscript numbers (which for sure can be configured somehow, too). Use a custom formatter expression for both axes:

case
when @grid_axis = 'x'
then
    CONCAT('[', floor(@grid_number/100000), ']',
        case
        when (@grid_number/1000 - floor(@grid_number/100000)*100) < 10 then '0'
        else ''
        end,
        @grid_number/1000 - floor(@grid_number/100000)*100)
when @grid_axis = 'y'
then
    CONCAT('[', floor(@grid_number/100000), ']',
        case
        when (@grid_number/1000 - floor(@grid_number/100000)*100) < 10 then '0'
        else ''
        end,
        @grid_number/1000 - floor(@grid_number/100000)*100)
end

Add Label Coordinates in MGRS

'32UMB' + to_string(floor(x(transform(make_point($x, $y), 'EPSG:4326', 'EPSG:25832')) - 400000)) + lpad(to_string(floor(y(transform(make_point($x, $y), 'EPSG:4326', 'EPSG:25832')) - 5600000)), 6, '0')

Tricks

• https://gis.stackexchange.com/questions/439645/best-practices-to-show-extent-of-print-composer-maps-in-main-canvas-in-qgis

Useful non-QGIS Resources

Coordinate Conversion

GeoConvert from package geographiclib-tools can be used to convert Google Maps LatLon to MGRS:

> echo 52.51627404556164, 13.377684321544193 | GeoConvert -m
33UUU8991619699

Also available online https://geographiclib.sourceforge.io/cgi-bin/GeoConvert or by shortlink https://is.gd/utmmgrs.

Note that Google Search results (which do not point to hostname maps.google.com) seem to lack the context menu for copying the coordinate?

GeoTIFF Merging

https://gis.stackexchange.com/questions/2195

GDAL_CACHEMAX=1024 gdal_merge.py -of GTiff -co COMPRESS=LZW -co BIGTIFF=YES -o all.tiff in1.tif in2.tif ...