topic Re: Why won't my layers align? in Data Management Questions

Why won't my layers align?

SarahFischer — Mon, 16 Sep 2019 04:50:53 GMT

Hi All,

I am undertaking a project utilising both ArcGIS and SAGA GIS. I have created a OBIA shapefile in SAGA that imports into ArcGIS but I can not get it to align with a point file I am using. This works fine in SAGA (the point file transforms and projects on-the-fly and layers perfectly well) but ArcGIS has some functionality that is better to query the map with so I would like to do this in ArcGIS. Try as I might, I can not get the layers to line up correctly.

The point file has the following GCS:

Geographic Coordinate System: GCS_Australian_1966
Datum: D_Australian_1966
Prime Meridian: Greenwich
Angular Unit: Degree

The OBIA file:

Projected Coordinate System: Transverse_Mercator
Projection: Transverse_Mercator
false_easting: 500000.00000000
false_northing: 0.00000000
central_meridian: 129.00000000
scale_factor: 0.99960000
latitude_of_origin: 0.00000000
Linear Unit: Meter

Geographic Coordinate System: GCS
Datum: WGS84
Prime Meridian: Greenwich
Angular Unit: degree

I'm surprised I'm having so much trouble as I've been using ArcGIS for a while without any issues like this.

Any suggestions would be gratefully received as this is really holding me up.

Kind Regards

Sarah Fischer

PhD student Charles Darwin University

Re: Why won't my layers align?

DanPatterson_Retired — Mon, 16 Sep 2019 06:01:43 GMT

Can you use the Project tool and apply the necessary datum transformation to get the files to align?

Also, just to make sure, add the UTM layer to an empty map (no basemap either) to ensure that the coordinate system of the map is UTM. Then add the point layer to see if project-on-the-fly works in that scenario. If it doesn't, do an actual projection of the coordinates to UTM applying the necessary datum transformation.

Re: Why won't my layers align?

MelitaKennedy — Tue, 17 Sep 2019 20:48:06 GMT

I think the problem is thegeographic coordinate system of the OBIA file. If you're reporting the name of the GCS correctly:

Geographic Coordinate System: GCS
Datum: WGS84

We're not recognizing the GCS as a "known" GCS so the point data using AGD66 isn't getting converted to WGS84. If you can't change the OBIA data's coordinate system to WGS 1984 UTM 52N using the Define Projection tool, try setting the map/data frame to it. Its WKID is 32652. That should allow you to set a transformation from AGD66 to WGS84 to line up the point data.

Re: Why won't my layers align?

SarahFischer — Wed, 18 Sep 2019 04:07:42 GMT

Thank you everyone for your input. What ended up working was changing the projection of the OBIA file in SAGA GIS and then importing it into ArcGIS. I just couldn't get it to transform going into ArcGIS directly.

Thanks again for all the suggestions.

Kind Regards

Sarah Fischer

PhD student Charles Darwin University