1:10 rasters with no spatial info

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This topic contains 4 replies, has 1 voice, and was last updated by  rok.geo 7 years, 1 month ago.

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  • #3410

    rok.geo
    Participant

    First of all, big thanks for all the data. Sure there’s loads of data on the net but most of it is inaccessible to GIS greenhorns (like myself) because of its format or similar reasons. This is why I’m happy to stumble on this service!

    I believe my question is a basic one so simply turning me in the right direction will do the trick. I would like to work with 1:10m raster images but I see that spatial reference info is not included.. What’s the easiest way to achieve this (using ESRI)? If I want to use this TIFF as a base map for a vector (points) layer that I already have and is in a specific coordinate system I should probably put the base map in the same coordinate system (projected and geographic)?

    Appreciating any input.

    Cheers!

    #4087

    Nathaniel
    Keymaster

    @Rok.Geo: You’re very welcome! The raster TIF files include a second world file that acts as a prj file for SHPs. With it you’ll be able to reference other themes on top of one of the Natural Earth rasters. If it is not projecting to your destination coordinate space, use define projection in Toolbox to set to geographic WGS84. ArcMap will then reproject for you.

    #4088

    rok.geo
    Participant

    Thanks for the quick response.

    Of the files included with the TIF file I reckon the tfw one is used for spatial referencing. But when I try to manually set the projection of the raster (or any other vector) file (either via ArcCatalog or through Define Projection tool in ArcMap) it does not show any file in the tif’s folder. It seems that it is looking for a prj file (also the case in Global Mapper). Should I be searching for a way to convert tfw into prj?

    If I understand correctly SHP files store spatial info in PRJ files while rasters store spatail info in TFW files (or in the header in case of geotifs). How come the included TFW is not recognized by ArcMap in this case?

    #4089

    Nathaniel
    Keymaster

    Good questions. Likely it’s not showing you the TFW as it’s not a data file in and of itself (kinda like an SHX file is never visible). With the TIF loaded, in ArcGIS Toolbox go to Data Management > Projections and Transformations > Define Projection. Then choose either import one PRJ files from the vector parts of Natural Earth or Select > Geographic Coordinate Systems > World > WGS 1984.prj. Some headers in the TIF have just the registration numbers, not the PRJ coordinate system. It sounds like your setup is either ignoring it, or it is not present in the right way.

    #4090

    rok.geo
    Participant

    Thanks for your help Nathaniel and keep up the good work!

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