Wednesday, August 19, 2009

Two New Gigapans, More on the Way

Our Owyhee River field area is very amenable to the gigapan. On my last trip I took the time to acquire several new GP images. Some are huge and still churning. But for now, check these out:

See the full gallery on posterous

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Wednesday, August 12, 2009

Yes. There is a sediment lens trapped between two flows in the West Crater Lava

It is at Dogleg Bar. You can see it as a squinty-eyes shaped discontinuity in the lava stack to the right/east of the terrace sequence. I got out there today to find out that the lens is comprised of weakly cross-stratified, moderately sorted, pea to pebble gravel composed entirely of cinders and fragmented vesicular basalt with a glassy outer rind. Fairly clear evidence for the river dealing directly with hot lava. I suspect that there are more examples of this. I tried to get to the big face in Qbw where the prominent fracture is located between Bogus Falls and Dogleg. Too steep and dangerous to peer over the edge far enough. The photo I have of that area from last May, however, is suggestive of a sediment lens akin to the one I visited today.

See the full gallery on posterous

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Sunday, August 2, 2009

Dogleg Bar figure with hillshade and profile

These were made in surfer and grapher. For further editing, the emf file can be modified in illustrator. Said file will be placed in shared folder.

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Distilling LiDAR data with ArcGIS

Turns out that ArcMap has some very useful tools buried in the toolbox for evaluating the basic characteristics of LiDAR data. For example, using the 3D analyst extension, it is possible to collate the basic parameters of *.LAS tile sets. For example, the following steps:

3d analyst > conversion > from file > point file information

will generate a polygon shape file of the data tiles and will atrribute each tile set with measures of point count, point spacing, max z, min z, etc. This is useful because it is nice to have a simple polygon file that shows the extent of the data and some of the metrics in the attribute table are important to have for applying other types of processing to the data. In the figure above, the tiles are labeled according to object id (OID) rather than filename because the filenames are exceedingly cumbersome.

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Saturday, August 1, 2009