I am trying to show in leaflet a geotiff raster image that was generated in gvSig. The basemap I am using in leaflet is a wms server with projection EPSG:3857.
Leaflet needs to know the upper right and bottom left corners in latitude and longitude coordinates which I get from the tfw file.
When I add my raster image the south west and north east corners are displayed in the correct position (the ones I specify to leaflet), but the other two are not. And most of the image is not displayed at the correct position either. It seems there is a problem with the projections.
gdalinfo of the raster file shows:
Driver: GTiff/GeoTIFF
Files: ModCombustible.tif
Size is 600, 945
Coordinate System is:
PROJCS["ETRS89 / UTM zone 30N",
GEOGCS["ETRS89",
DATUM["European_Terrestrial_Reference_System_1989",
SPHEROID["GRS 1980",6378137,298.257222101,
AUTHORITY["EPSG","7019"]],
TOWGS84[0,0,0,0,0,0,0],
AUTHORITY["EPSG","6258"]],
PRIMEM["Greenwich",0,
AUTHORITY["EPSG","8901"]],
UNIT["degree",0.0174532925199433,
AUTHORITY["EPSG","9122"]],
AUTHORITY["EPSG","4258"]],
PROJECTION["Transverse_Mercator"],
PARAMETER["latitude_of_origin",0],
PARAMETER["central_meridian",-3],
PARAMETER["scale_factor",0.9996],
PARAMETER["false_easting",500000],
PARAMETER["false_northing",0],
UNIT["metre",1,
AUTHORITY["EPSG","9001"]],
AXIS["Easting",EAST],
AXIS["Northing",NORTH],
AUTHORITY["EPSG","25830"]]
Origin = (713179.879402380902320,4381253.375599999912083)
Pixel Size = (5.001750158730428,-5.001750158730441)
I tried to use gdalwarp to reproject the raster in EPSG:3857 with the command:
gdalwarp -t_srs EPSG:3857 ModCombustible.tif ModCombustible_3857.tif
but in the tfw file I am getting negative UTM easting coordinates which doesn't make any sense to me.
What should I do to properly show the raster image in leaflet?
EDIT: The negative easting coordinates are correct for the EPSG:3857 if they are west of London. Using the link provided by the user30184 I could translate the coordinates to latitude and longitude and show the image at the correct position.
EDIT2: To clarify basic concepts which were not clear to me: as IvanSanchez mentioned in the comments, UTM (Universal Transverse Mercator) is a system of 60 different projections using false easting and northing. In the other hand Web Mercator (EPSG:3857) is not UTM but uses easting and northing coordinates to define a position. It is the de facto standard for web map applications.