Shape Files &
Coverage
Efficiency:
The most efficient way to conduct an Aerial Survey is to have a Shape File of the property preloaded into a Garmin, or comparable GPS before the flight ensues. The Shape file outlines the properties’ legal boundaries defined by fences, roads, etc.
The legal boundaries are typically on file with a local FSA or NRCS Agency.
If the property is on Texas Parks and Wildlife Managed Lands Deer Permits Program, the legal boundaries will be defined and plotted on a map which is accessible to The Landowner by logging into the Landowner Management Assistance System (LMA), and accessing their Ranch’s information.
Once inside The LMA System, the landowner can click property information, scroll down to the map and download the .KML Shape File for the property. There will a “download as .KML” at the bottom of the page, below the map.
Shape Files:
A shape file is typically generated in .KML which is Google Earth’s file format. Landowners can find their fence lines on Google Earth and trace them out using the path function.
The lines can be directly placed over fence lines or boundaries, creating a path outlining the property boundaries. The .KML file can typically be converted over a to a .GDB or .GPX Format which can be loaded into a GPS for deployment in the helicopter.
As of 2017, when creating a Texas Parks & Wildlife Land Owner Authorization Form (LOA ), a map of the property, in either .kml or gpx, must be provided so the shape file can be loaded into The TWIMS System for LOA approval.
Predefined Transect Lines and Spacing:
Preset transect lines can be overlaid on an existing shape file to pre-determine coverage rates. Alternate transect lines should be generated for the property to account for wind and weather changes. A set of both east/west, as well as north/south transect lines should be generated if predetermined coverage rates and transects are desired. While North/South Transect Lines are desired as to avoid flying into the sun, they are impractical on a day with excessive North/South Winds.
The alternative, and most common practice, is to extract miles traveled from The GPS Odometer to determine percentage of coverage.
Aerial Survey Coverage Rates & Acres Flown per Hour:
The amount of ground the helicopter can cover per continuous flight hour varies greatly with terrain, cover and the animal’s behaviour on the particular day. The first hour is always the slowest, allotting for aircraft warm-up and in-flight area orientation.
In mesquite country, after the leaves have fallen, it is possible for the helicopter to cover in excess of 2500 acres/hr.
In contrast, once the trees have bloomed, this number can be cut in half to roughly 1200/hr. Thick cedars and deep canyons present their own problems, coverage rates are usually contingent upon available light. On the other side of the spectrum, open country, as more typified in the areas of West Texas, coverage rates can exceed 5000 acres/hr.
Excessive picture taking leads to decreased coverage rates. Further complications can be the animal’s unwillingness to move, leading to tighter grid pattern and slower speeds. It has been my experience that there is no remedy on days when the animals refuse to cooperate. Either the timing in the day is off, or it is a futile effort. These cases are rare, and the surveying will be suspended and rescheduled.
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Location
Breckenridge, TX
Serving the Cross Timbers, Lubbock, Panhandle and surrounding areas.