Use of Ground Control Points
The best way to Decide In Case Your Drone Mapping Task Needs GCPs
Ground control points (GCPs) may be a useful tool for aerial mapping. Once used properly, they assist guarantee a high degree of worldwide accuracy, that is vital for many measure and construction comes. however the actual fact is, the bulk of drone maps don’t need GCPs due to this, it’s vital to grasp once to use communication system points and once to skip them. However however does one decide if your drone mapping project desires GCPs?
In an earlier post, we tend to wrote about using communication system points to improve the accuracy of aerial maps. Today, we tend to take a glance at what sorts of aerial maps take pleasure in communication system points and why mistreatment them could or may not be vital for your next project.
When to Use Ground Control Points
In general, there area unit 2 reasons to use GCPs: if you wish a high degree of worldwide accuracy, or if you’re shrunken to supply measurements inside a particular vary of accuracy. If your project needs a high degree of worldwide accuracy, then you ought to use communication system points. Land surveys and DOT road inspections area unit 2 samples of comes that need true world accuracy.
Ground control points have been important to Bon Air Drone’s Shelly Engle once she used aerial mapping to generate a relief map of a quarry in Virginia. Strategically placed GCPs helped Shelly make sure the map had a high degree of worldwide accuracy. This was vital once she orthorectified the ultimate relief map.
As Bon Air co-owner Kyle Falwell puts it, this level of accuracy sets their company except for the competition. “Our prime priority is that the internal control aspect of it,” says Kyle. “There area unit lots of individuals out there doing aerial surveys, however we wish to hold our hat on accuracy.”
Likewise, GCPs area unit vital if you employ AN aerial map to require meter or linear measurements and you are contracted to supply those measurements inside a particular vary of accuracy. This can be the case for several applied science and construction comes, wherever 1/10 foot accuracy is commonly needed.
Construction Company Brasfield & Gorrie considers the aim of every map before deciding whether or not to use GCPs. “If we’re planning to create a essential determination off of the info set, fully we’re planning to use GCPs,” says VDC organizer Hunter Cole. “If it’s a lot of for a promoting effort or we’re creating smaller relative meter measurements, we tend to might not hassle with GCPs on website.”
If you’re unsure regarding mistreatment GCPs, inspect our short diagram below. it’ll quickly assist you decide if they’re necessary for following project you’re engaged on.
GCPs once a Surveyor’s Signature is required
If your aerial mapping project needs a surveyor’s signature, you ought to use communication system points. Measure firms usually use GCPs as a result of a high level of worldwide accuracy is vital to their work.
Common measure comes wherever communication system points area unit helpful include
Property boundary surveys: Accuracy is crucial here, as a result of property boundary surveys area unit typically the last word in mete disputes. An aerial map may be accustomed compare plat information and confirm if a mete has touched.
Insurance assessments: A ideal of this can be a Federal Emergency Management Agency survey for flood insurance, that uses correct elevation information to work out a property’s flood risk.
Subdivision and new construction surveys: Local and federal laws typically need surveys so as to document the presence of utilities like gas and power lines, or water mains.
General liability: If structural injury happens to a building, it’s doubtless a case are going to be filed against the contractor United Nations agency designed it. Having survey records that show the structure was designed up to code helps shield the contractor from being control liable.
Using communication system Points to Prove the Accuracy of Measurements
In general, once you use a map to require meter or linear measurements inside a map — say, to live stockpile volumes or the length of a fence — ground management points aren’t necessary. In most cases, as long because the resolution of a map is sweet, the margin of error for measurements goes to be identical with or while not GCPs. this can be as a result of there’s a direct correlation between high-resolution pictures and sewing accuracy. Following a couple of best practices will facilitate make sure you manufacture high-resolution maps.
That being same, engineering and construction still use communication system points, even for maps that don’t need world accuracy and don’t want a surveyor’s signature. In several cases, contracts need that measurements taken on a project fall inside a particular vary of accuracy. Communication system points might not do abundant to extend the accuracy of measurements, however a decent thanks to prove that these measurements are correct.
Best Flight Practices once mistreatment GCPs
If you choose communication system points area unit the proper alternative for your aerial mapping project, following step is selecting the simplest flight parameters and following best practices to make sure the accuracy of your map. Ultimately, your flight parameters can rely on your mapping subject, however here area unit some general tips to stay in mind once mistreatment GCPs.
250–350 feet for many maps: This vary can offer you a decent quantity of resolution, however won’t abate the sewing method with too several pictures.
400 feet for giant comes: For particularly giant maps, like within the biological science business, a better altitude is critical. Less resolution is required for this kind of map, and a better altitude allows you to cowl an oversized space quickly whereas aggregation enough information relative to the tallest feature within the map.
75/75 overlap recommended; don’t exceed 85/85. Higher overlap will increase accuracy, however an excessive amount of overlap slows down process speeds unnecessarily.
Ground-truthing with vertical checkpoints
Ground-truthing your information is extremely vital to make sure the accuracy may be replicated mistreatment multiple strategies.
Taking a couple of check shots helps you verify that you just area unit seeing the proper output. It additionallyoffers you another variety that you just will stand by once presenting the accuracy of your map.
Before technique your map in Drone Deploy, you need to input the EPSG code that relates to your GPS measurements. opt for your EPSG code by means of modifying the settings of your GPS measuring deviceIn most cases, we tend to advocate mistreatment WGS84 (EPSG: 4326). One exception is once you have to be compelled to compare your aerial map to existing plat information from a previous land survey. therein case, make certain to gather information within the same frame of reference that was used once the first land survey was taken.