Saturday 16 February 2019

qgis - Experiencing transformation anomalies when performing a Save As to convert coordinates between NAD83-Z14 and NAD27-Z13


Good morning all:


I have recently discovered QGIS and have been hoping to find a solution for converting bacthes of xy coordinates between two projection systems for our mapping system. I have known good coordinates for both datums that I am trying to convert between, but even though I believe I'm doing the right steps in QGIS, my coordinates are still out by a small margin, which is where my question begins...


Prior to finding QGIS, for single coordinate conversion I have been using the free Java-based Coordinate and Data Transformations tool that is available on the internet from Charles L. Taylor. I've attached an image of the two known coordinates from this tool.


**As my rating does not allow image posting, I've provided the text data of my coordinates. If anyone wants to see the images, please reply and I can e-mail them.


Original coords in NAD83/WGS84 Zone 14N (EPSG:4326)


Lat/Long: 49.362977,-101-742026
UTMs: x 300914.226, y 5471423.864

Converted coords in NAD27 Zone 13N (EPSG:26713)



Lat/Long: 49.362924,-101.741634
UTMs: 736577.110,5472689.933

So from here, I had imported my list of coordinates (original datum is NAD83/WGS84) into QGIS to get my list of points. After adding the corresponding UTM coordinates using the Export/Add Geometry function, I can see that the UTMs in the attribute table are the same as my original .csv file.


After conversion to what I thought was NAD27-Z13 using QGIS, my first coordinate comes back with the following coordinates:


Lat/Long: 49.36297733,-101.74205733
UTMs: 736548.431,5472694.612

When I plot the above coordinate on the map I have with the known good points already on the map, obviously they don't line up. What I'm wondering is if I'm missing a step or if there are options that must be set during conversion. From what I can tell of QGIS, if I can find a solution to this, it will make batch conversion between datums much quicker. Many of the coordinate files that I receive are in .csv format and QGIS seems like the perfect application for what I need, however, I'm hoping that someone that has more experience can point me in the right direction.


Thanks in advance for any and all replies, Jeff M





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