Global Mapper v25.0

CADRG Export quality

MartinRS Global Mapper User
edited April 2015 in Raster Data
After creating overlays for airspace and exporting to an RPF (JNC/TPC/JOG) there is a significant degradation of image quality. Is there any way to rectify this?


  • MartinRS
    MartinRS Global Mapper User
    Here is an example of the quality degradation:

    On the left is the after, right is before.

    Also, I notice that this tile is named 003v80e3.tp1, but when creating the new tile with vector data overlaid, the file name becomes 003V801Z.TP1. I could go through and rename all the tiles what they are supposed to be, but that would be time consuming. Is there any way to change this behavior?
  • MartinRS
    MartinRS Global Mapper User
    I just noticed v17 is out. Is any of this fixed?
  • Mykle
    Mykle Global Mapper User Trusted User
    Martin, Your needs use processes that are not simple (tiled exports). While I have used a couple of them (mbtiles and osmtiles), I don't have relevant comments for you. I am more familiar with "normal" exports to single files. That said, I would want to have local files for the area of interest, whether downloaded within Global Mapper from on-line web services and exported to local files, or complete files downloaded and loaded separately. So these files will likely be at the maximum available resolution. Look at the metadata for each of your local files to determine the resolution of each file. When all files are local, then I can close all on-line layers, load the local files, and add additional content. Exported data may use defaults of the layer with the least resolution, so you may need to adjust. Again, you need to know the resolution of each of your layers. I don't see much difference between your samples. Both have image quality issues at that resolution. If this response doesn't get you going, then Bob's frequent post is appropriate: "I recommend getting the latest release of Global Mapper and try loading your data. If the problem persists in the latest release, then your best bet is to send an e-mail describing your workflow, your sample data, and the results to Blue Marble Geographics support ( This will ensure that the support team sees the problem and can determine the solution. Thank you." Good luck, Mykle
  • MartinRS
    MartinRS Global Mapper User
    edited October 2015
    I realize that there can be quality issues, but seriously, look at this. It's almost unusable in the jet. 

  • Mykle
    Mykle Global Mapper User Trusted User
    Yes, this sample clearly shows a difference in resolution.

    The question is "why?".  At least for this investigation, isolating each of your processing steps will help.  We are especially interested in the output resolution settings that you have used for each export.  What export format are you selecting to create your RPF?  

    For those of us reading your comments, we can't tell the source of your two sample images.  For the high-resolution sample, are we looking at the layer that has been directly downloaded from on-line sources?  Have you defined a local source for GM to read your exported map tiles, and that's what we're seeing with the low-resolution sample?  

    Are you working with map layers directly downloaded from on-line sources, or have you exported your project area to local raster file(s) at your target resolution (or better) and then loaded them?  

    You should be able to turn off or unload your on-line layers, and work with your local files and verify that you have (at least) the resolution you require.  

    Then you can export your tiles from local files.  

    Again, you are interested in finding the step where the maximum resolution has been reset to a value with less resolution.  We are certainly interested in these effects that may affect our own projects.  


  • MartinRS
    MartinRS Global Mapper User
    So, I'll try to go through this line by line and answer everything.

    This is a TPC (1:500000) that I downloaded from NGA's GDP.

    Export format is RPF, and after selected export I choose the TPC option which matches the downloaded map scale.

    None of my layers are online, so I'm not sure what you mean by: Are you working with map layers directly downloaded from on-line sources, or have you exported your project area to local raster file(s) at your target resolution (or better) and then loaded them?  
  • Mykle
    Mykle Global Mapper User Trusted User
    Okay, that helps.  Thanks.

    While I am not able to find a site that provides CADRG downloads, I won't be able to attempt to reproduce your issue.  (I'd like an address, if you can provide one)

    You have downloaded files, and are then loading them into Global Mapper.  So the potential on-line issues are not relevant.  

    I note that CADRG is not one of Mike's favorite topics, at least partly due to requirements by some viewer programs that the data files must be wrapped in an (unnecessary) extra layer of complex formatting.  

    I do see CADRG/CIB/RPF as a raster output option.  (it's not a web format as I was thinking)
    I also see where you specify the Chart Type as "CADRG - Tactical Pilotage Charg (1:500,000)"
    That choice determines the filename extension.  

    Given the lack of an option to specify a resolution, those specs must be built-in with the export options.  

    My guesses are that the resolution for this choice (at least) is set too large, and/or
    that there are issues with implementing the CADRG compression methods.  

    Mike was using the original spec (1996).  He was provided with an update, so perhaps he didn't get into all of the resolution issues since the original poster was satisfied with the results of the changes made by Mike.  Perhaps that also affects a filename convention that may not be reflecting current specs.  

    It looks like after you export the TPC, you can load the files back in, and are presented with the resolution contrast problem.  

    Looks like it is time to upgrade this issue.  So I'll repeat Bob's frequent post that requests you send sample data and procedure to so that the support team sees the problem and can determine the solution.  

    I will certainly be interested in their findings.
    I used these maps, once upon a time, long long ago (before digital!).  All paper.  Would certainly have liked the capabilities that we have today.  I am still known to cover a wall with some of these!  


  • I've been looking for ways to improve CADRG exports and ended up on this old thread. The only way I seem to be able to improve quality of let's say a GEOTIFF to CADRG conversion is to downscale the map eg. if the GEOTIFF is a 1:500k export it to a 1:250k CADRG. I haven't found a way to bring the map scale back up without losing quality again..