State DOTs Turn to Aerial Surveys to Save Money
State DOT personnel are looking more and more to aerial platforms when it comes to highway design and rerouting because it means less boots on the ground.
International geospatial giant Merrick & Co., together with Midland Surveying of Maryville, Mo., recently provided airborne LiDAR services to the Missouri Department of Transportation (MoDOT) on two major highway projects.
The first project, which was completed last year, included planimetric compilation, terrain modeling, orthoimagery, ground surveying and LiDAR services at nine separate sites scattered across the state. The second project, for which acquisition data was compiled recently, included 10 sites from Kansas City to St. Louis. Together, the two projects covered 140 miles of highway. All of the aerial data was collected by helicopters.
Three different types of data were collected on each segment of road. The data contained three different LiDAR densities with average corridor widths of 600 feet. The densest data collected was 120 points per square meter, and it focused on terrain right up to the edge of the pavement.
Utilizing aerial platforms is nothing new to MoDOT; it has been doing it for years. What makes these projects different is the density of the data collected. “We have worked with DOTs across the country, and it is unusual for a DOT to want data that dense,” says Brian Holzworth, the Merrick & Co. project manager for those two contracts. “But this is a trend we are seeing–not just with DOTs, but customer-wide. Higher density data paints a much better picture of what is going on.”
Holzworth said Merrick used the Optech ALTM Orion C200 airborne scanner with the Applanix 510 POS/AV Inertial Measurement Unit and Trimble’s TAC Pro 60 megapixel RGB Digital Camera CCD array to complete the tasks.
The reason for the requested density is two-fold, according to Brad McCloud, land survey coordinator for MoDOT. In addition to the safety of its field crews on major highways, MoDOT’s driver for using aerial platforms is financial.
“Over the past two years, we have reduced our field survey crews by 30%,” McCloud says. “We knew we could obtain the accuracy we needed with fewer crews by obtaining denser data.”
MoDOT is able to supplement the aerial data with its own terrestrial crews, who can use field scanners to collect additional information when needed. This reduces the amount of surveying required to be conducted internally and, in turn, the number of field crews needed on staff.
“Talking to other DOTs, no one is hiring in (their) surveying departments. Everyone is looking for anything that can supplement (personnel),” McCloud says. “Like everyone else, we are finding ways to do more with less.”