The 2005 Elevation Project included delivery of two products: a Digital Surface Model (DSM) and a Digital Elevation Model (DEM). The DSM is a 5-foot post spacing full surface model (with buildings, trees and vegetation). The DEM is a 5-foot post spacing near bare earth model (with buildings, trees and vegetation removed). Both are tiled to 4000x4000 feet, and cover the entire state.

The surface was autocorrelated from two ADS40 black and white sensors. The near bare earth was also automatically generated, and has a few issues with buildings and spurious cones and holes.

The DEM will hold 10-foot contours "as-is", and may be able to support 5-foot or 2-foot contours with stereo confirmation and the addition of 3D breaklines from photogrammetric compilation using stereo pairs (which are available from the acquisition vendor, EarthData, for a fee).

Availability

1. Contact your county emergency management agency (click here for a list of recipients).
2. Download the files for free from the Indiana Spatial Data Portal.
3. Purchase individual counties on disk from the IGIC online store.
4. For information on purchasing statewide sets, contact the IGIC offices at 317.489.0091 or info@igic.org.

Digital Surface Model (DSM)

Resolution: 5-foot post spacing (variable based on terrain)

Projection: Indiana State Plane coordinates East or West Zone, NAD83/NAVD88 datum

Data Format: Imagine .IMG Format

Delivery Method: One set on external hard drive and one set on DVD delivered to State; one individual county set on DVD delivered to each county. Using the ISTAR processing system, we are able to generate an accurate, high resolution digital surface model by auto-correlation of the stereoscopic imagery. Using the acquired digital imagery and ISTAR work flow, an automated digital surface model (DSM) is generated.

This process provides three key advantages advantages: 1.) Known accuracy, 2.) Cost effectiveness, and 3.) Consistent, seamless and current.

Each pixel location is measured multiple times resulting in a much higher level of horizontal and vertical accuracy when compared to the traditional film/scanning approach. The ISTAR processing system computes the X,Y,Z value for each DSM post utilizing every stereo angle collected from the data. The final DSM generated with the ISTAR process is a “reflective surface DEM," providing elevation data on above-ground features including buildings, trees and vegetation. This DSM is used to adjust the raw ADS40 imagery.

Digital Elevation Model (DEM)

Resolution: 5-footr post spacing

Projection:Indiana State Plane coordinates East or West Zone, NAD83/NAVD88 datum

Data Format: Imagine .IMG Format

Delivery Method: One set on external hard drive and one set on DVD delivered to State; one individual county set on DVD delivered to each county. The Digital Surface Model (DSM) is processed to a “near bare earth” DEM, using tools that are also used for LIDAR reflective surface DEM editing. The DEM is perfectly co-registered with the orthophotography products. This product is suitable for a variety of applications, including:

1. Orthorectification of the ADS40 imagery, and for subsequent orthorectification of aerial imagery created by any jurisdiction (i.e., future orthophotography and GIS projects will “fit” together)
2. Automatic extraction of 10-foot contours
3. Statewide 6-inch and 1-foot resolution orthophotography can support accurate 5-foot or 2-foot contours with further photogrammetric processing (not a delivery of the 2005 Orthophotography Project)

All DSM and DEM products share a common control network. Known accuracy allows for enhancements. With further photogrammetric processing, stereo confirmation and break lines can be compiled from stereo pairs to correct and supplement the DEM mass points to support topographic mapping, surface modeling and floodplain mapping applications.