Using 'TACK' points for scaling data sets

JoeKJoeK Global Mapper UserPosts: 9
edited August 2013 in Technical Support
I'm using Global Mapper v12.02.

In order to convert from UTM coordinates to GROUND coordinates, we apply a scale factor derived for the center of the project.

I can apply a scale factor to the data set in Global Mapper by using FILE=> EXPORT VECTOR FORMAT => TEXT FILE => COORDINATE OFFSET/SCALE. This process scales the data from coordinate 0,0. Is it possible to scale the data from a "TACK" point located in the center of the data set? In other words, rather than scaling data from point 0,0, I'd like to scale it from a random coordinate other than 0,0.

The reason for this is that surveyors can localize to the UTM coordinate of the TACK point, and then apply the scale factor and collect/lay out data in ground coordinates rather than GRID coordinates. This is done so the design of the project can be done in ground coordinates rather than on the UTM grid.

I know that in the dialog box right below the SCALE FACTOR entry, there is an entry for OFFSETS FOR X/Y/Z VALUES, however this shifts/offsets the coordinates rather than centers the scaling on the new coordinate, and applying a offset is not the same as scaling to a non origin coordinate.

Any ideas?

Question 2: Is the application of the SCALE FACTOR to a data set anywhere else other that a "Text File"?

Thanks.

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited August 2013
    You can right-click on a layer in the Control Center and select the SHIFT option to transform the coordinates. This allows a few different ways to shift, including one where you specify a transformation including a scale factor and offset. Note that the Rotation origin is also the scale origin (I will update the dialog box in the latest v14 to reflect that).

    Another approach is to just setup the projection such that the scale and offset are what you want. It sounds like you have a different situation of an additional scale on top of base UTM coordinates though so it might not be possible to model as a single projection definition, although an Orthographic projection centered at your new grid origin with an appropriate scale factor might be extremely close. The State Plane projection has built-in support for extra scale factors and origins on top of the base projection system.

    Thanks,

    Mike
    Global Mapper Guru
    geohelp@bluemarblegeo.com
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
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