Sunday, April 29, 2018

Impressive Lidar Resolution Aids Field Work

Regular readers of this blog know that lidar imagery and elevation models are a regular feature of posts on the Washington Landscape. That is in part because utilizing lidar is a routine part of my work. Lidar has been a bit of a revolution for geology as well as land use planning.

New high resolution lidar was released earlier this year by the Washington State Department of Natural Resources. The lidar coverage is part of a program to obtain high quality lidar coverage for much of the state. The new lidar covers areas that previously had no lidar and also covers areas where lidar was available, but was of lesser quality. 

The newer lidar data sets have amazing resolution that allows for spotting land features on the order of a foot or two in scale. I utilized the new high resolution lidar recently on a couple of small-scale projects.  

2006 lidar

2017 lidar

There is an obvious difference in the sharpness of the lidar images between 2006 and 2017. The arrow in the second image from 2017 points to a feature completely obscured in the 2006 image. The feature appears to be an erosion feature. 

Erosion feature
A small ravine eroded into slope from water discharged on to the slope from an uphill road ditch

The erosion feature was not the site I was looking at. But seeing it in the lidar before going out in the field suggested that I might get a good exposure of the underlying geology units on the hill slope, Indeed, I did get a good view of the underling glacial related sediments exposed in the small ravine.

What is impressive is how small this ravine is. The feature is only a couple of feet across and five feet deep at its deepest and yet very apparent in the new lidar.   

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