As a young surveyor-in-training, the most common way I’ve seen GPS technology used is in data collection, where GPS can be really advantageous in reducing the number of field personnel needed to complete many jobs.  Once, my company used three-man crews, and then we were down to two, and now we can use only the occasional one-man crew.   In fact, just the other day I obtained the last bit of information I needed in the field using our GPS roving unit without having to have a crew called back to the office and rerouted for the rest of the day.

I’ve also seen some of the disadvantages.  Unless you plan carefully, you can waste valuable time if, once you get to a site, you realize that you will not be able to use GPS due to poor satellite availability, or geometry, or even terrain limitations.

Some of the limitations can be dealt with though. To determine if the site itself is a possible candidate for GPS data collection, I often check the aerial photography provided by online county GIS maps to look at the contours as well as the tree cover.  To determine if it’s an optimum time to collect data, we can input site-specific information as well as the date and time of day we are planning to collect data into software, which helps us forecast our satellite availability as well as our projected DOP (dilution of precision) values. 

I’ve found that a combination of GPS data collection with total stations, as well as ample planning, are the best bet for assuring the most expedient completion of a project.

—Ashley Rose-Nalin

PSM Columnist

The Sanborn Map Company has added a new dimension to their library of digital data by assembling nearly 100 cities of 3D building models for international and domestic locations.

The product, "Sanborn 3D Cities," includes 3D geometries of buildings, terrain models, and orthophoto products of Manhattan, Chicago, Seattle, Vancouver, Rio de Janeiro, and more. In total, Sanborn has over 500,000 buildings in its archive today with plans to expand, update, and collect new cities on a continual basis.

Once you select a geographic area, you can easily access project details including federal funding amount and description. The application also allows searches according to U.S. DOT agencies: aviation, transit, maritime, highways, and rail.  See the map here. 

Scientists working on understanding the integration of space and time will gather in California February 22–23, 2010, to attend the Space-Time Modeling and Analysis Workshop. The workshop will be part of the first Redlands GIS Week—a gathering of thought leaders from academia, government, and industry to advance the science and application of geospatial technologies.

Researchers are invited to submit 500-word abstracts describing the work that they would present as either a keynote or lightning (focused 10-minute) talk. Preference will be given to abstracts describing concrete results to concrete problems, and software demonstrations are encouraged. (Image credit: Tony Tyson, UC Davis and LSST Corp.)