Plan It Autodesk

LIDAR

LIDAR refers to Light Detection and Ranging. It uses the same principles as RADAR. A lidar instrument sends a light pulse out to a target. The time required for the light to be reflected back to to the instrument can be used to determine the distance to the object.

Why is this important to land planning? Because this is the new, preferred method for obtaining highly accurate topography. Instead of the traditional aerial photogrammetric techniques, which have been marginally improved with the move to digital cameras, LIDAR is the new system of choice because among other reasons it is an active system that captures an extremely dense grid of points. Plus, it can be used with leaves on the trees, although it can be a challenge to differentiate return signals from tree tops and bare ground, especially in dense canopy.

For reference an excellent discussion of LIDAR topographic surveys is provided at http://www.csc.noaa.gov/products/sccoasts/html/tutlid.htm and http://www.sbgmaps.com/lidar.htm

LIDAR can be used day or night, depending on the project the costs can be less than traditional photogrammetric topographic surveys, and the turnaround can be much faster.

Next time - The ASLA Annual Meeting October 6 -10, Minneapolis, MN

Image Data Sources for Planning - Vol. 4

In the last post we looked at the mid-range of geo-image data suppliers. At the high end of the value chain is where we find the largest data creators and aggregators in the world.

Let's start with the data creators. This category includes the major aerial and commercial satellite firms worldwide. In the US two of the largest aerial mapping firms are Aerial Cartographics (www.aca-net.com) and AirPhoto USA (www.airphotousa.com). The Big 3, in terms of satellite imaging are DigitalGlobe (www.digitalglobe.com), a french company, Spot Image (www.spotimage.fr), and GeoEye (www.geoeye.com), the recent combination of Space Imaging and Orbimage.

Digitalglobe's bird (as they like to call it) is Quickbird, Spot has is Spot 3D, and GeoEye has Ikonos and Orbview 2 and 3. There is a constant jockeying for leadership position among these companies, and although they want to develop the commercial markets, they live off the government.

In the data aggregator category the big dog is GlobeXplorer (www.globexplorer.com), who in fact offers products from many of the above companies. In addition, the satellite firms also have agreements with aerial mapping firms to provide them with data when the satellites cannot deliver. Of course, GYM - Google Earth, Yahoo Maps and Microsoft Live have to be included here as well.

Next time - LIDAR

Image Data Sources for Planning - Vol. 3

Last time we looked at some of the original providers of digital map and image data. This time we are going to focus on the next level of sophistication - on line viewing/delivery of geo-image data.

Once again, it was the USGS that was instrumental in jump starting this delivery channel through their agreement with Microsoft. The latter was looking for an extremely large database that they could use to demonstrate the power of their software. The USGS entered into a CRADA with Microsoft to provide the entire DRG database, and www.terraserver.microsoft.com was born.

Of course, today this does not seem like a big deal thanks to GYM, but at the time it was pretty impressive, assuming you had the bandwidth to download the images.

Today, www.topoozone.com, www.terraserver.com and www.i3.com, as well as GYM, to name just a few, cannot only provide on line viewing, and download, but also web streaming services that can provide your firm with instant access to vast libraries of map and image data worldwide.

Next time - Image Data Sources for Planning - Vol. 4