topic Reprojecting Elevation Data in ArcGIS Enterprise Portal Questions https://community.esri.com/t5/arcgis-enterprise-portal-questions/reprojecting-elevation-data/m-p/258474#M3506 <HTML><HEAD></HEAD><BODY><SPAN>Hey there, this is my first time posting in the forums and I have a bit of a tricky question.&nbsp; Hopefully somebody will be up to the challenge of answering it (or at least providing some insight).</SPAN><BR /><BR /><SPAN>I'm currently working on a research project attempting to detect changes in elevation between Digital Surface Models.&nbsp; My base imagery is a LiDAR scan in .asc format with accompanying orthoimagery.&nbsp; The LiDAR is projected in Transverse Mercator from GCS MGI in the Bessel 1841 spheroid and D_MGI datum.</SPAN><BR /><BR /><SPAN>My "Time 2" imagery is a DSM (in .tif) and accompanying orthomosaic (in .tif) and 3D point cloud (in .txt).&nbsp; These are projected in Transverse Mercator from GCS WGS84 with WGS84 spheroid and datum.</SPAN><BR /><BR /><SPAN>I can reproject co-register the imagery (using Erdas Imagine) no problem.&nbsp; The problem is that due to the nature of the data, when reprojected, only horizontal data is reprojected.&nbsp; The vertical data (stored as pixel values) is unaffected.&nbsp; This comes as no surprise.&nbsp; So while my two datasets can line up perfectly in the horizontal plane, my WGS84 DSM is, on average, about 50 meters higher than the MGI DSM (LiDAR).</SPAN><BR /><BR /><SPAN>My question is: how can I reproject, or modify, my raster based DSMs so that the elevation values are consistent?&nbsp; Differencing the two rasters to detect elevation change would be pointless when they are in different Geographic Coordinate Systems.</SPAN><BR /><BR /><SPAN>I also have a set of GPS points I collected in the area with a RTK rover unit.&nbsp; The points were collected in WGS84 and exported in both WGS84 and MGI formats.&nbsp; When compared against their locations in both rasters, their elevation readings are accurate between 20cm and 1m.&nbsp; I need to difference these two rasters and show the viability of the elevation change detection, but am stuck at this juncture.&nbsp; Does anyone have any insight as to how I can solve this problem?&nbsp; Thank you for reading and thinking.</SPAN><BR /><BR /><SPAN>Cheers,</SPAN><BR /><SPAN>Christopher</SPAN></BODY></HTML> Mon, 20 Aug 2012 08:40:27 GMT ChristopherChavis 2012-08-20T08:40:27Z Reprojecting Elevation Data https://community.esri.com/t5/arcgis-enterprise-portal-questions/reprojecting-elevation-data/m-p/258474#M3506 <HTML><HEAD></HEAD><BODY><SPAN>Hey there, this is my first time posting in the forums and I have a bit of a tricky question.&nbsp; Hopefully somebody will be up to the challenge of answering it (or at least providing some insight).</SPAN><BR /><BR /><SPAN>I'm currently working on a research project attempting to detect changes in elevation between Digital Surface Models.&nbsp; My base imagery is a LiDAR scan in .asc format with accompanying orthoimagery.&nbsp; The LiDAR is projected in Transverse Mercator from GCS MGI in the Bessel 1841 spheroid and D_MGI datum.</SPAN><BR /><BR /><SPAN>My "Time 2" imagery is a DSM (in .tif) and accompanying orthomosaic (in .tif) and 3D point cloud (in .txt).&nbsp; These are projected in Transverse Mercator from GCS WGS84 with WGS84 spheroid and datum.</SPAN><BR /><BR /><SPAN>I can reproject co-register the imagery (using Erdas Imagine) no problem.&nbsp; The problem is that due to the nature of the data, when reprojected, only horizontal data is reprojected.&nbsp; The vertical data (stored as pixel values) is unaffected.&nbsp; This comes as no surprise.&nbsp; So while my two datasets can line up perfectly in the horizontal plane, my WGS84 DSM is, on average, about 50 meters higher than the MGI DSM (LiDAR).</SPAN><BR /><BR /><SPAN>My question is: how can I reproject, or modify, my raster based DSMs so that the elevation values are consistent?&nbsp; Differencing the two rasters to detect elevation change would be pointless when they are in different Geographic Coordinate Systems.</SPAN><BR /><BR /><SPAN>I also have a set of GPS points I collected in the area with a RTK rover unit.&nbsp; The points were collected in WGS84 and exported in both WGS84 and MGI formats.&nbsp; When compared against their locations in both rasters, their elevation readings are accurate between 20cm and 1m.&nbsp; I need to difference these two rasters and show the viability of the elevation change detection, but am stuck at this juncture.&nbsp; Does anyone have any insight as to how I can solve this problem?&nbsp; Thank you for reading and thinking.</SPAN><BR /><BR /><SPAN>Cheers,</SPAN><BR /><SPAN>Christopher</SPAN></BODY></HTML> Mon, 20 Aug 2012 08:40:27 GMT https://community.esri.com/t5/arcgis-enterprise-portal-questions/reprojecting-elevation-data/m-p/258474#M3506 ChristopherChavis 2012-08-20T08:40:27Z