Global Mapper Pro

Four Corner Rectification Wizard

Matt
Matt Global Mapper UserTrusted User
edited May 2011 in Suggestion Box
I imagine there are quite a few of us that spend a lot of time rectifying rectangular maps of known scale and known corner coordinates. The typical process is select a corner, enter coordinates, and then repeat that task for the other corners. Very tedious, especially when a lot of maps are involved.

Was thinking that GM could make that task much easier. Instead of having to enter coordinates for all four corners on the map, how about a wizard where we enter the coordinates for one corner, select the scale (which would be remembered for the next one) and then just click on the other three corners. GM would then automatically calculate the coordinates for the other 3 corners.

Comments

  • Geo
    Geo Global Mapper User Trusted User
    edited April 2011
    hello Matt,

    this can be done il you select 2 corners (it's better to select opposite corners)

    see "Batch Rectification", "Add Control Points at Corner Points", "Remember Last Projection", "Ctrl+Left Click Recenters and Zooms Other View" in Image Rectification (Georeferencing)

    you can also provide GCP (Ground Control Point) with "File Menu" / "Load control points from a File" or even create a .gmw file.
  • Matt
    Matt Global Mapper User Trusted User
    edited April 2011
    None of those do what I'm suggesting since the maps often have collars and the known lat/lon points are not the actual corners of the image. Plus even with your suggestions one would still have to manually type in 4 sets of lat/lon coordinates. With what I'm suggesting, we would only have to enter a single set of lat/lon coordinates, then click 3 more points on the map and would have 4 points of reference with associated lat/lon coordinates for each.

    Selecting only two corners rarely works as well as entering coordinates for all four corners when dealing with scans.
  • global_mapper
    global_mapper Administrator
    edited April 2011
    Matt,

    What exactly would you be entering for the scale value you are referring to? A map scale wouldn't be exact enough since no projection can exactly represent the 3D surface of the earth so the actual scale of a map as compared to ground truth will vary between the X and Y directions and often be slightly different on different parts of the same map.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • redbeard
    redbeard Global Mapper User Trusted User
    edited April 2011
  • Matt
    Matt Global Mapper User Trusted User
    edited April 2011
    Yes, something along the lines of what Redbeard suggested. I'm thinking it would primarily be for standard small scale maps. 7.5', 15', 30', etc. Should be a great benefit to anyone that has to sit down and georeference dozens or 100s of small standard-scale raster images.
  • global_mapper
    global_mapper Administrator
    edited April 2011
    Matt,

    I can add this to the todo list, I can see how the coordinates could be automatically calculated once you specify a scale and start coordinate so long as you click on each corner. In redbeard's other thread it sounds like he ended up using the Global Mapper grid display and snapping capabilities to easily get coordinates snapped to the desired location without having to type a bunch of coordinates. I think this wouldn't end up being much more work than specifying a scale.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • Matt
    Matt Global Mapper User Trusted User
    edited April 2011
    Thanks....I hadn't thought of using the grid display. Will give that a try also.
  • redbeard
    redbeard Global Mapper User Trusted User
    edited May 2011
    Matt, Mike,
    I recently saw this software while reading about the USGS effort to reference maps. Article here http://www.vector1media.com/spatialsustain/the-usgs-dusts-off-their-archives-and-prepares-for-digital-release.html and the software here http://www.geography.wisc.edu/research/projects/QUAD-G/

    Basically it allows for nearly automated referencing of topo maps or others with a regular Lat/Lon spacing.
  • redbeard
    redbeard Global Mapper User Trusted User
    edited May 2011
    I just tried to reply, but the post didnt show, so if two show up, that's what happened.
    Take a look at this http://www.geography.wisc.edu/research/projects/QUAD-G/
    Automatically georeferences the images (with prior setup and planning).
    I found it while reading about the activities of USGS. http://www.vector1media.com/spatialsustain/the-usgs-dusts-off-their-archives-and-prepares-for-digital-release.html
  • global_mapper
    global_mapper Administrator
    edited May 2011
    Looks like interesting software, although it wouldn't work for general-purpose automatic rectification, only automatic rectification of those images with the characteristics of 7.5' topo quad maps.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
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