Graphics Reference
In-Depth Information
AUTHORITY["EPSG","6167"]],
PRIMEM["Greenwich",0],
UNIT["degree",0.0174532925199433],
AUTHORITY["EPSG","4167"]],
...
As you can see, the downloaded basemap uses the
New Zealand Transverse Mercator
2000
coordinate system. We need to translate this into the WGS84 (geographic latitude/
longitude coordinate) coordinate system so that we can use it in the ForestTrails program.
To do this, we'll use the
gdalwarp
command, like this:
gdalwarp -t_srs EPSG:4326 basemap.tif basemap_wgs84.tif
If you look at the resulting image using
gdalinfo
, you'll see that it has been converted
into the lat/long coordinate system:
Coordinate System is:
GEOGCS["WGS 84",
DATUM["WGS_1984",
SPHEROID["WGS 84",6378137,298.257223563,
AUTHORITY["EPSG","7030"]],
AUTHORITY["EPSG","6326"]],
PRIMEM["Greenwich",0],
UNIT["degree",0.0174532925199433],
AUTHORITY["EPSG","4326"]]
Note
You might wonder why we didn't download the file directly in the WGS84 coordinate sys-
tem. We downloaded the file in its original CRS because this gives us more control over
the final image. Reprojecting the image ourselves also makes it easier to see how the im-
age was changed when it was reprojected.
So far, so good. However, if we look at the resulting image, we'll see another problem:
