Archived: July 29, 2004


Mission Creek is on of three major creeks that run into Compano Bay, Texas. The creek originates west of Refugio, Tx and is part of the San Antonio River watershed.

At the mouth of Compano Bay, the creek is contains many salt marshes and is surrounded by bluffs with local elevations of up to 40 feet. (Quite high for coastal areas)

TOPSAR data was acquired over Mission Creek June 29, 1996 in an effort to improve digital elevation models dem of the region.

DOQQ-derived Digital Elevation Model

The image to the left is the DOQQ-derived digital elevation model of Mission Creek at the mouth of Mission Bay. Note the Mission Creek, in black, as it winds its way to Mission Bay. The marshes immediately adjacent to Mission Creek are indicated by blue.

Benefits of TOPSAR

There are several reasons for investigating the use of TOPSAR for high resolution topography. The first reason is TOPSAR is an instant digital product which does not rely upon human interpretation of aerial photography in order to create a digital elevation model. In addition to the dem, the TOPSAR product also includes radar imagery in the C-VV and L-VV bands. This additional imagery makes the dem a more meaningful product since it can be easily registered with other datasets for analysis - therefore implementation of models will improve.

TOPSAR can create elevations with an accuracy from 60cm in the near-range to 1.25 m in the far range. This is an improvement from current elevations available from aerial photography. Current dem's of the area created by USGS digital orthoquadrants show elevation contours at 5 feet intervals.

The TOPSAR data does, however, have some effects that must be corrected before the elevation models are acceptable. Navigational effects from the aircraft (pitch, roll, and yaw) can enter slight variations in the radar signal which can affect the end result. These factors can be eliminated by fitting a regression model to represent the topography and verifying it with a few GPS points.

TOPSAR product show above includes two bands of polarimetric radar, C-VV and L-VV, as well as the digital elevation model.


Sunday, 01-Aug-2004 00:24:38 CDT