1

I have both TINs and LiDAR data for an entire county, divided into a grid of multiple tiles. I want to generate contours from this data at 2 foot intervals, using ArcGIS 10.5.

I decided to do this by first generating an elevation raster using TIN to Raster, and then running the Contour tool to create contours from the raster.

The problem is that the resulting contours have a gap where the tiles meet. The width of the gap is equal to the cell size I specify when creating the raster.

How can I eliminate this gap and get contours that are seamless across tiles?

Would it be better to start with the LIDAR data instead, or would I still encounter a similar problem?

| improve this question | |
  • I´m not 100% certain, but I assume the gap appears somehow due to the rasterization prozess and the anchor position of each tin vertex for the respective cell, possibly by the combination of first creating the tin from raster and then rerasterize the tin...anyways, if you have LiDAR data, which should be interpreted as raster already, why not using them directly? maybe creating a mosaic database first to guarantee a seamless coverage. problem here could, of course, be the data's size, but maybe arc can handle it... – geozelot Jun 14 '17 at 11:51
  • are you sure the tiles for both data sets are actually seamless? – geozelot Jun 14 '17 at 11:58
  • @ThingumaBob I don't think the TIN was created from a raster, I think it was created from LIDAR data, but I'm not sure since both were given to me. I'm sure the tiles are seamless - I've experimented and found that the gap between tiles is exactly the width of the cell size I specified when converting TIN to raster, so it must be a result of that process somehow. It looks like the contours end half the cell distance away from the edge of the raster, because they're interpolated from the elevation at the center point of each raster cell. – Matt Leonard Jun 14 '17 at 13:39
  • @ThingumaBob If i wanted to start the process with the LIDAR data instead of TIN, would you happen to have any more advice on how to go about that? Thanks! – Matt Leonard Jun 14 '17 at 13:53
  • hm...what format is your LiDAR data? check out the mosaic dataset creation (for example desktop.arcgis.com/en/arcmap/10.3/manage-data/raster-and-images/…). you should then be able to simply create contours from that dataset with the standard tools. – geozelot Jun 15 '17 at 6:29
1

Would it be better to start with the LiDAR data instead?

Yes, it would. Here is the processing workflow:

From here, there are at least two options:

  1. As pointed out by Jae, directly generate contours from filtered Las Dataset Layer with Surface Contour tool **.
  2. Or generate a DEM with the LAS Dataset to Raster tool *. Then, create contours from the DEM raster ***.

Choose option one if you are sure the intermediate output raster will not be needed in further/parallel tasks.

* In basic license, requires 3D Analyst or Spatial Analyst..
** Requires 3D Analyst..
*** Requires 3D Analyst or Spatial Analyst.

| improve this answer | |
  • 1
    If you have access to the 3D Analyst extension, contours can be created directly from a LAS Dataset (lasd) using the “Surface Contour” tool in ArcGIS. desktop.arcgis.com/en/arcmap/10.3/tools/3d-analyst-toolbox/… – Jae Sep 2 '18 at 0:01
  • You can apply filters to your LAS Dataset (or create a filtered LAS Dataset layer) and the tool will honour the filter, as all other LAS Dataset tools in ArcGIS. Additionally, if you are finding ground contours noisy, you could try creating your contours from only “model key points” (class 8), but mileage may vary on the quality of the output. – Jae Sep 2 '18 at 0:23
  • 1
    Thanks... I am at a different job now so I don't have time to try this workflow, but it sounds like it is probably what I should have done in the first place. – Matt Leonard Sep 5 '18 at 19:19

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.