ACPF DEM Download
The ACPF Development Team at the USDA/ARS National Laboratory for Agriculture and the Environment, in cooperation with the North Central Region Water Network (NCRWN), are pleased to announce the release of version 2 of the Agricultural Conservation Planning Framework (ACPF), with enhancements to both the Toolbox and the Database. The new release and accompanying information is available on the ACPF home page, on the NCRWN web site at http://northcentralwater.org/acpf/.
To supplement this project, the ISUGISF has created a tool to download 2 meter DEM by watershed for the state of Iowa. Click here to use the tool. In order to download, you will be asked for some identifying information. This tool will NOT work with MIcrosoft Edge or Internet Explorer, we recommend using Chrome or Firefox.
The Iowa HUC12 2m DEM database was derived from the original lidar point cloud and processed through ArcGIS using the following steps:
- Lidar point-cloud to points to TIN
- TIN to raster with pyramid thinning
- Conversion to integer cm Z values to address quantization error
- Pit filling to remove one-cell sinks
- Hole punching to remove small (<=10cm) depressions in the DEM
This process results in the P-Class of HUC12 elevation models. This collection has been augmented by performing a partial hydro enforcement using the IA DNR’s stream centerline to create the S-Class library. The process of preparing the stream centerlines for use in hydro modification is as follows;
- Stream features are extracted from the state-wide feature class for the HUC12 watershed
- Features are generalized using the SimplifyLine method using the Bend_SIMPLIFY algorithm and a 10m tolerance
- Resulting features are split at vertices to create individual features with no intermediate vertices
- Very short segments, <= 8.5m, are merged where possible
The resulting features are used as cut lines when an obstruction to flow is present in the DEM that should be "burned through", such as a culvert which routes flow beneath a road. The centerline data were developed from a 1m DEM so there are some minor flow compatibility issues, but the time savings that is realized when involved in the hydro conditioning phase of the toolbox is significant. Average size of the HUC12 2m DEM in a 7Zip archive is 75Mb.