Qgis

24 Jan 2024

Quick and dirty geographic longitude offset for GIS

Convert GIS data with Lat/Lon (EPSG:4326/WGS84) coordinates with longitude in the range 0-360 to -360-0 to cover -180-180 in a GIS envrionments map with this quick and dirty custom proj-style projection string.

The custom projection definition is +proj=longlat +ellps=WGS84 +towgs84=0,0,0,0,0,0,0 +pm=-360 +no_defs

This can be used as follows,

  1. load a spatial dataset with Lons defined in the 0-360 range,
  2. duplicate or load another layer with the same dataset,
  3. set layer in 1. CRS to WGS84 or EPSG4326,
  4. and set layer in 2. to a custom CRS using the projection definition above.

This process results in the dataset covering the -360 to 360 Longitude range (and implcitly -180 to 180 as well) between the two layers which can be used in a variety of different project coordinate reference systems or projections. Switching +pm=-360 to +pm=+360 will go the opposite way from (-180-180) Lons to (0-360) if necessary, because that parameter sets or modifies the default Prime Meridian Longitude in degrees-East.

11 Oct 2023

*ugrid* ADCIRC vectors in QGIS with MDAL

use nco cli to make compliant files

29 Mar 2023

MDAL

MDAL Logo

The Mesh Data Abstraction Library (MDAL) out of OSGeo is a “translator library” for many common conventions found in meteorology and hydrology. The library supports data found in Grib and NetCDF encoded as NetCDF Climate and Forecast Metadata Conventions (CF) or Unstructured Grid Conventions (CF/UGRID) and represented as geospatial mesh data. In addition to supporting mature and well-defined spatial data encodings in self-describing files, the library also supports numerous model-specific formats including Telemac, HEC-RAS, and TUFLOW.