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Shapefiles projecting incorrectly with local coordinates and combination factor

KaitlynAbrahamson

I am trying to project several shapefiles created in CAD that show up too far north. The projection in CAD is North Dakota North, International Foot with County Ground Coordinates. I have them projected in NAD 1983 StatePlane North Dakota N FIPS 3301 (Intl Feet) coordinate system right now and the projection is Lambert Conformal Conic. I'm not sure why the map has that projection. The CAD files also have a combination factor of 1.0001075116 and I'm not sure if that is why the shapefiles are not projecting in the correct location. Does anyone have any suggestions to help me?

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pokkiri

Local coordinate systems with combination factors can be tricky because the data often doesn't align with standard CRS definitions. The first step is always to verify where the data actually appears on a map.

A quick diagnostic approach: upload your shapefile to https://projectionfinder.comProjection Finder - it previews your data on a basemap so you can immediately see if it's appearing "too far north" or in the wrong location entirely.

If the visual location is way off from where you expect, the CRS definition is likely incorrect. For CAD data with local coordinates, sometimes you need to work with the surveyor or data provider to get the correct transformation parameters.

The visual verification step saves a lot of trial-and-error when dealing with non-standard coordinate systems.

danretired

If you are doubting the cad files, I would start there. Nothing is going to go well if you have suspect data going in

KaitlynAbrahamson

Do you think the CAD files are off? This happens quite frequently because the files I'm working with are made with local coordinates that rarely project correctly. Unfortunately, this happens a lot and I'm forced to move them manually when I can.

KaitlynAbrahamson

I tried what you described and added the shapefile to a new map. It came in projected in the correct coordinate system, but the file is still over 50 ft off where it should be. Is there something else I can do? I don't want to have to move it manually.

danretired

50 feet is a datum issue.

To mitigate the apparent non-moving issue, you should add data to a map with no other data because the first layer that is added to a map sets its coordinate system. Add other data after.

If your data doesn't have a defined coordinate system in the first place or one you are unsure of, then that is an important step. Examine the coordinate system via its properties.

Project should only be used once a shapefile has a defined coordinate system... a correct coordinate system, since defining something wrong will only make matters worse.

After using the Project tool, you can compare it to known/trusted data for placement... if it is off by 50 feet then it was defined wrong.

KaitlynAbrahamson

When I use Define Projection instead of Project, the files do not move with either tool. I'm trying to establish a system to work through this each time it happens. It happens fairly often when I get shapefiles with local coordinates and combination factors.

KaitlynAbrahamson

It is only maybe 50 feet off.

JayantaPoddar

Keep a copy of your original data (one with North Dakota North, International Foot ) before moving forward.

Please check what happens if you use Define Projection (instead of Project tool) with NAD 1983 StatePlane North Dakota N FIPS 3301 (Intl Feet) [if the latitudinal extent of the data is between 47.15 to 49.01 DD].

Please check what happens if you use Define Projection (instead of Project tool) with NAD 1983 StatePlane North Dakota N FIPS 3302 (Intl Feet) [if the latitudinal extent of the data is between 45.93 to 47.83 DD]

danretired

is it a meters vs feet too far north, or a small amount that may be datum related?

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