Drone surveying basics

[Arun]

Hi

Our compeny is investigating the ability to complete drone surveys of landscapes with the aim of creating 3D models to be used in AutoCAD for measurment purposes - these will be for surveys of watercourses to assess their viability for hydropower projects. Accuracy needs to cm level - max 10cm for outline survey or cm level for design work.

I understand to get this accuracy level we need to use RTK GPS to be able to set out Global Control Points (GCP) visible by the drone. Being a complete novice to this I have a couple of questions, would greatly appreciate some comments.....

We were thinking of using a DJI Drone.

Firstly, I presume we need to make obtain accurate coordinates and elevation of all the GCP's which we can do with an RTK base/rover.

Secondly, do we also need RTK GPS on the drone itself, or can software create a 3D model if the drone can see and reference GCP's from the air?

Thirdly, are there any special camera requirements for what we need to do, beyond that available on lets say a DJI Phantom 4?

We were thinking of using software like Pix4D software to create the model and then Autocad ReCap to get it into AutoCAD....

Would greatly appreciate someone giveing me an overview of the components needed to acheive the desired result.

Thanks ever so much for your help...

Arun

 

[GMack]

Personally, I'd look more towards a drone that is used for survey work if you want that sort of accuracy. DJI, imho, just isn't that accurate along with often buggy software or hardware compared to something like a Trimble or Kespry and others who work in conjunction with AutoCAD. I think Trimble's survey drone works with AutoCAD. Kespry uses their own Cloud-based server and mapping in 2D and/or 3D and is pretty much an automated flying drone and software. You just draw out the area and it self-flies, and then auto uploads the data upon landing and they take over the making of the maps. Bad part is it is costly at around $30K yearly on a lease, but it is a turn-key system and frees you from needing to play for hours or days in mapping software. The Trimble may be more affordable and outright purchased.

Goggle "Drones for surveying." Lots of options out there.

 

[Meta4]

Secondly, do we also need RTK GPS on the drone itself, or can software create a 3D model if the drone can see and reference GCP's from the air?
Thirdly, are there any special camera requirements for what we need to do, beyond that available on lets say a DJI Phantom 4?
Would greatly appreciate someone giving me an overview of the components needed to acheive the desired result.

You don't need RTK GPS on the drone if you are using GCPs.
A phantom camera will be just fine, the P4 pro is extremely good.
The commonly used apps are very easy to use and are very good at planning and capturing the imagery.
You need to be familiar with operating the Phantom first before trying these.

Here are two that are worth looking at:
DroneDeploy: Powerful Drone & UAV Mapping Software
Drone Mapper Imagery Processing
Dronedeploy has a forum and you'll find answers to a lot of questions there.

Here's a quick example of an orthophoto I flew today - 13 acres, about 3 mins flying, 84 images

13 acres, about 3 mins flying, 84 images
Full size = 21000 x 16000 pixels.

 

[BigAl07]

If you want CM level work you'll need RTK.

The new DJI Matrice210RTK is the drone for that work but it comes with a hefty price tag. You'll be dropping $13K before you even add the camera/sensor assembly.

FlyHighUSA - Matrice 200 Series
DJI’s First Ever Enterprise Level Aircraft is Here!!!

 

[bluelight support]

The new DJI Matrice210RTK is the drone for that work but it comes with a hefty price tag. You'll be dropping $13K before you even add the camera/sensor assembly.

Ive been looking into this as mapping is our bread and butter - from what i understand this is based on the RTK system DJI used for the Matrice 600 which indeed gives CM accuracy but they information is not fed through the flight controller to the camera therefore the CM accuracy is only for flight and not to give cm accurate x,y, and z into the exif info in the jpg file

 

[bluelight support]

We were thinking of using software like Pix4D software to create the model and then Autocad ReCap to get it into AutoCAD....

Would greatly appreciate someone giveing me an overview of the components needed to acheive the desired result.

Arun - we do a lot of mapping and have been using an inspire 1 pro with 12mm olympus lens to get quality images. We then use Geo 6000 to get between 4-8 ground control points to 1-3cm. Input images from the Inspire into Photoscan Pro, Drone2map or 3d survey, and calibrate images to GCPS. Can get accurate DEM and measurements to a couple of cm. Cheapest way to go without going eBee route, and then eBee is 5cm accurcate

 

[bluelight support]

as a footnote I'm mainly active on the Inspirepilots.com so you can see loads of messages on there re mapping and surveying!

 

[Richard R]

Maps Made Easy has similar software. Depending on the height that you fly the mission, pixel size ranges from around 2 cm to 5 cm. Point to point accuracy (distance between two points in a map) is pretty good, on par with the pixel size. Absolute location of the map on the surface of the earth is limited my GPS accuracy. However, MME does allow you to identify a GCP in several images and to input the more accurate position info for it that is then used to more accurately locate the map. the map can be created as either a visible image or rendered as a 3D. you can output the data in several formats including .las or .xyz.

 

[JayinSC]

Aloha Arun. Hope this helps

Mapping Drones | 3DR Site Scan - Commercial Drone Platform

SOLO Mapper – Aerial Vista

MAPIR CAMERA

REACH RTK KIT — Emlid

(yes, 3dr has "readjusted" its company)

 

[PeteM]

Phantom 4 is cheap, well supported and easy to use.

In my opinion is the perfect drone for this kind of work and "on the field" does not have much to envy to the drones that cost 10 times more.

The "problem" of the Phantom 4 used for surveying purposes resides in the "software ecosystem" that comes as standard and personally I feel I can not recommend ready-made solutions as DroneDeploy or MapsMadeEasy because they are expensive, commercial and very little customized to individual needs.

I tried many solutions, and for me the best was the (open source) Mission Planner. For the flight I advise you to use the app Litchi.

The 4 Phantom camera is also fine for photogrammetric purposes BUT you have to put in place various "precautions" both during flight and post-processing to get a good precision... at that point you just need few GCPs and all will be fine

 

[Nicrophone]

Do GCP have to have a gps coordinates previously marked or can you use non GPS GCP and still get accurate data? Sorry total newbie when it comes to GCP

 

[bluelight support]

Do GCP have to have a gps coordinates previously marked or can you use non GPS GCP and still get accurate data? Sorry total newbie when it comes to GCP

I see from your website your offering mapping already, what is your current workflow and what post processing software are you using ?

 

[cadm8]

Flying with a p3p, using ultimate flight for way point flights and using RTK GCPs. Everything is manually designed but I've come to the conclusion that this is the only way to be sure you will not be returning to the same survey site twice. Processing with Agisoft photoscan. P4p camera looks to be a beast much better than the p3p, so given the fact that we're achieving 3-4cm level accuracies, it can only get better with the p4p

 

[bluelight support]

Flying with a p3p, using ultimate flight for way point flights and using RTK GCPs. Everything is manually designed but I've come to the conclusion that this is the only way to be sure you will not be returning to the same survey site twice. Processing with Agisoft photoscan. P4p camera looks to be a beast much better than the p3p, so given the fact that we're achieving 3-4cm level accuracies, it can only get better with the p4p

What ground station equipment are you using to get 3-4cm accuracy ?

 

[cadm8]

What ground station equipment are you using to get 3-4cm accuracy ?

GPS RTK for GCPs and total stations for ground surveys. The checks (actually tests) can be performed as we have surveyed common points between the two methods (building corners, Heights or checkpoints like low walls, pavement corners etc)

 

[jthomps]

There are a few courses online starting to pop up on how to properly use drones for survey work. Those might be worth looking at.

Just remember that if you have vegetation on the ground (grass, bushes, etc) you are only getting the top of this vegetation when you use photogrammetry. You might have 5cm accuracy on clear ground or at the GCPs, but you won't have this around the water courses you're looking if they are covered in tall grasses.

If you need precise ground elevations you're still better off using that RTK equipment to survey the ground!

Sent from my Pixel using PhantomPilots mobile app

 

[skyacramer]

I heard a lot about Kespry Drones for Aggregates | Kespry

 

[cadm8]

There are a few courses online starting to pop up on how to properly use drones for survey work. Those might be worth looking at.

Just remember that if you have vegetation on the ground (grass, bushes, etc) you are only getting the top of this vegetation when you use photogrammetry. You might have 5cm accuracy on clear ground or at the GCPs, but you won't have this around the water courses you're looking if they are covered in tall grasses.

If you need precise ground elevations you're still better off using that RTK equipment to survey the ground!

Sent from my Pixel using PhantomPilots mobile app

True! You must always be careful what your method limitations are and not ask for things that cannot be supported by your chosen survey method...

 

[Nicrophone]

I see from your website your offering mapping already, what is your current workflow and what post processing software are you using ?

I currently use drone deploy for automated flight, then upload to their cloud software for processing, AVG flight hight is 125'

 

[bluelight support]

Thats a good solution, another one to look at is maps made easy, their free map pilot app is great and their business version which in the uk is £38 allows terrain adjustment, and a number of other options. Their cloud service is free for images under 250 so its good to try as well.

Other than that we do everything off-line where you have much more control. We upgraded from Phantom 4 to Inspire 1 Pro with 12mm olympus lens, and have sold than and just got an Inspire 2 as we wanted better quality.

Running at 125ft gives you a good resolution.

The new phantom 4 Pro is also meant to be a good solution with the mechanical shutter and bigger sensor.