Before you sign a drone survey proposal, read past the price. Most developers don’t, and it costs them. A drone survey that looks clean on paper can produce outputs a county rejects, a lender won’t accept or a permit office sends back for recertification.

You don’t need to be a pilot to review a drone survey contract well. You need to know which things to check and what to do when they’re missing.

What a Drone Survey Proposal Should Always Include

A solid proposal covers more than scope and price. Before comparing quotes, confirm each proposal answers these questions clearly:

• What sensor will be used (camera or LiDAR)?
• What flight altitude is planned?
• Will ground control points be placed on site?
• Is RTK or PPK positioning included?
• Who will certify the final survey output?
• What file formats will you receive?

If a proposal skips any of these, ask. A firm that can’t answer clearly is already telling you something.

Photogrammetry or LiDAR: Why the Method Matters

These are the two main methods used in drone surveys. They’re not interchangeable.

Photogrammetry stitches together hundreds of overlapping photos into a 3D model. It works well on open sites with clear ground visibility. It’s also less expensive than the alternative.

LiDAR sends laser pulses at the ground and measures how long they take to bounce back. It penetrates tree canopy and dense vegetation to reach bare earth below. For wooded or heavily vegetated sites, that’s the only method that gets you accurate terrain data.

If your site has significant vegetation and the proposal only mentions photogrammetry, ask why. On the wrong site, photogrammetry produces a model of the treetops, not the ground you’re building on.

What “Accuracy” Actually Means in a Drone Survey Proposal

This is where proposals get vague fast.

A drone survey using RTK positioning and proper ground control can hit horizontal accuracy of 1 to 3 centimeters. That’s survey-grade. Without ground control, standard GPS gives you 1 to 3 meter accuracy. That fails most permit reviews. Commercial lenders won’t accept it either.

Look for these terms in the proposal:

• RTK or PPK positioning (centimeter-level accuracy)
• GCP-verified (confirms ground control was used)
• Standard GPS only (not survey-grade, ask why)
• “Sub-foot accuracy” with no positioning method named (too vague, ask for specifics)

If the proposal doesn’t name the positioning method, close that gap before you sign.

Ground Control Points: The Line Item Many Proposals Skip

GCPs are physical targets placed on the ground before the drone flies. The surveyor measures their exact coordinates, then uses them to verify and correct the drone data during processing.

Without GCPs, even an RTK drone can drift by several feet across a large site. The error tends to concentrate at site edges, which is exactly where boundary and setback calculations matter most.

A complete proposal tells you:

• How many GCPs will be placed
• How they’ll be distributed across the site
• How they’ll be measured (total station, GPS rover or NTRIP network)

One GCP per 20 to 30 acres is a reasonable standard for most topographic surveys. ALTA-grade work requires more. If the proposal mentions zero GCPs and your project involves permits or construction staking, get a clear explanation before moving forward.

Who Certifies the Final Output?

This is the question most developers never ask. It’s also the most important one.

An FAA Part 107 certificate lets someone fly a drone commercially. It does not qualify them to certify a survey. In most states, any survey output used for legal purposes, permit filings or construction must be signed and sealed by a licensed Professional Land Surveyor (PLS or RPLS).

Check the proposal for one of these:

• A named licensed surveyor who will review and stamp the output
• A statement that the output will be certified by a PLS
• Reference to state licensure or compliance with ASPRS accuracy standards

If the proposal comes from a drone-only company with no licensed surveyor listed, the output may not be usable for your purpose. Confirm this before you pay.

If your project sits in a flood zone, also ask whether the licensed surveyor on the team can prepare an elevation certificate. That’s a separate document, but the same certified surveyor handles both. 

What Files You’ll Actually Receive

A drone survey can produce several different output types. Not all firms include all of them by default and some charge extra for specific formats.

Common outputs include:

• Orthomosaic map: a geometrically corrected aerial image of the full site
• Point cloud: a 3D dataset of millions of measured points across the terrain
• Digital Terrain Model (DTM): shows only the bare earth surface, used for grading and drainage design
• Digital Surface Model (DSM): includes everything above ground, including trees and structures
• Contour lines: derived from the DTM, used in civil engineering and site planning

Know what your engineers and permit office need before you accept a proposal. If the proposal only mentions an orthomosaic and your civil engineer needs a DTM for drainage design, you’re going back for more work.

Red Flags to Spot Before You Sign

These items in a proposal should make you slow down.

No positioning method named. RTK, PPK or standard GPS should be stated clearly. Vague accuracy claims without a named method are a warning.

No GCPs on a large or vegetated site. RTK alone isn’t enough for survey-grade accuracy on complex terrain.

No licensed surveyor listed. If the output needs to be certified and no PLS is named, the output may be unusable for your application.

Unusually fast turnaround. Most quality drone surveys with proper processing take 1 to 3 weeks. A 48-hour promise on a large site is worth questioning.

Output formats not specified. You need files your civil software can actually open. Confirm this before signing.

Questions to Ask Before You Sign

Run through this list before approving any drone survey proposal:

• What sensor are you using and why is it right for my site?
• What positioning system do you use, RTK or PPK?
• How many GCPs will you place and how will they be measured?
• Will a licensed surveyor certify the final output?
• What file formats will I receive and are they compatible with my civil software?
• What’s the turnaround from authorization to final delivery?
• What can delay that timeline?

Direct answers tell you whether the firm knows what they’re doing. Vague answers tell you the same thing, just the other way around.

Frequently Asked Questions

What should a drone survey proposal always include?

A complete proposal should state the sensor type (photogrammetry or LiDAR), the positioning method (RTK or PPK), whether GCPs will be placed, who will certify the final output and what file formats you’ll receive. Any proposal missing these details needs clarification before you sign.

Does a drone survey need a licensed surveyor?

In most states, yes, if the output will be used for permit filings, legal purposes or construction. An FAA Part 107 certificate allows someone to fly commercially but does not authorize them to certify a survey. Look for a named licensed Professional Land Surveyor in the proposal.

What is the difference between RTK and standard GPS in a drone survey?

RTK corrects GPS data in real time using a base station or network correction service and achieves centimeter-level accuracy. Standard GPS without correction gives 1 to 3 meters of accuracy, which is not suitable for survey-grade work or permit submissions.

What are ground control points and do I need them?

Ground control points are physical targets placed on site before the drone flies. A surveyor measures their exact coordinates and uses them to verify the drone data after processing. They’re standard practice on most sites where survey-grade accuracy is required.

How long does a drone survey take?

Most standard drone surveys take 1 to 3 weeks from authorization to final output. LiDAR surveys and large commercial sites take longer due to added field work and processing. Always get a written timeline before signing.