Computing transformation parameters
Scotty
Global Mapper User
Given two ASCII files of X,Y coordinates in which each file has a differnt point of origin, orientation, and scale is there a function in GM that will compute the affine transformation parameters and save them?
For example, a client has provided a series a data points in a local plane projection. If I determine the NAD83 UTM coordinates for those points (the project area of coverage is typically a few sq km), I'd like to be able to use GM to define the transformation parameters, so when new points are added with UTM coordinates, I can derive the corresponding local plane projection values.
This function should allow me to derive an overdetermined solution and examine the residuals of the transformation and remove any that do not meet expected accuracies and/or identify blunders.
EDIT... I can do this using Excel, but it would be useful to be able to do it with GM.
For example, a client has provided a series a data points in a local plane projection. If I determine the NAD83 UTM coordinates for those points (the project area of coverage is typically a few sq km), I'd like to be able to use GM to define the transformation parameters, so when new points are added with UTM coordinates, I can derive the corresponding local plane projection values.
This function should allow me to derive an overdetermined solution and examine the residuals of the transformation and remove any that do not meet expected accuracies and/or identify blunders.
EDIT... I can do this using Excel, but it would be useful to be able to do it with GM.
Comments

You can do this using rectification in Global Mapper. Just rightclick on a layer to transform in the Control Center and select to modify the layer position. Then enter control points to define the transformation. Under the Options menu on the rectification dialog you can choose the rectification method to use (Affine is one of them) and also display the transformation equations if you need that for something.
Let me know if I can be of further assistance.
Thanks,
Mike
Global Mapper Support
support@globalmapper.com
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