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Inspire 2 X4S for Survey Topo Maps

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I'm a licensed land surveyor & certified pilot. I'm trying to decide on whether or not to purchase the Inspire 2 with X4S or the P4P. I need to do high accuracy (elevations within 0.05'-0.10') topographic mapping in order to calculate dirt volumes for payment. I have all of the equipment needed to set GCPs. I need to know if the Inspire 2 or P4P would be stable enough in 10-20 mph winds to get pics good enough for the accuracy I need? I'd prefer to use the cheaper bird if it can handle the wind.
 
Hello @Bourne2fly

I think you would find them both fairly stable in the wind...my bigger concern is the requirement to have an elevation consistent from roughly half an inch or an inch. For a non-RTK system that is not much room for error and not something you will be able to even visually see.

Lots of people use this type of equipment for the use you are describing, but I am not sure it can perform perfectly at the spec you have identified.
 
I thought the rtk just helped with the horizontal orientation of the site. Does the rtk help nail down the elevations as well? Do you think the M200 or 600 would meet the spec?
 
I have all of the equipment needed to set GCPs. I need to know if the Inspire 2 or P4P would be stable enough in 10-20 mph winds to get pics good enough for the accuracy I need? I'd prefer to use the cheaper bird if it can handle the wind.
If you already have gps for gap you can already make accurate point clouts etc - which software will you be interpreting data with ?

We went for the I2 which had a better wind profile (in my humble opinion compared to the P4 which we also have) - we went I2 so we could use the X5S which with the 12mm Olympus lens at 120ft can give less than 1cm/px ground resolution, that coupled with post processing gives 0-5cm accuracy at 98 per cent with PFO of that most points were within 1cm
 
I thought the rtk just helped with the horizontal orientation of the site. Does the rtk help nail down the elevations as well? Do you think the M200 or 600 would meet the spec?
Yes, RTK will also help control the vertical position as well. It gives you incredibly accurate positioning. However, the M600 without RTK is extremely good as well. I am sure the M210 RTK will also be very accurate in its horizontal and vertical position. The RTK definitely adds some cost, but it does a really good job.

@bluelight.support has some real world experience that may be useful to you.

If you definitely need the vertical height to hold to an inch or less variation, you will probably have to go to an RTK system. If you can live with more than that, the Inspire 2 would be a good choice.

Let us know if there is anything else we can help with or if you are interested in a quote on any systems.

Thanks!
 
If you already have gps for gap you can already make accurate point clouts etc - which software will you be interpreting data with ?

We went for the I2 which had a better wind profile (in my humble opinion compared to the P4 which we also have) - we went I2 so we could use the X5S which with the 12mm Olympus lens at 120ft can give less than 1cm/px ground resolution, that coupled with post processing gives 0-5cm accuracy at 98 per cent with PFO of that most points were within 1cm

I'm planning on using either Pix4D or Trimble's UAS Master for processing.

In regards to the camera, I've been told that there's not much of a difference between the X4s & X5s for what I'm going to use it for. Do you think the X4s would work or is the X5s needed for this type of work?
 
We do mapping and surveys, and i do intend to get the X4S as a backup camera as it allows a longer flying time, and its a 1" sensor - I expect you'll be fine. Have you thought about 3D Survey as thats great for measurements.
 
I am a surveyor as well. I use the phantom 4 pro. I get 0.05' accuracy verified by sample cross-sections doing roadway and commercial sites with my drone. I've been thinking of an upgrade to the i2 pro with the x5s. However with the results I get from the phantom 4 pro since it has the 1" cmos sensor I don't quite know if there would be an enhancement noticeable. As for the Gps... I have yet to hear of a drone that's places the Gps coordinate at the focal point of the camera and thus the resulting data is not survey grade even with the RTK drones. It's not like a Gps antenna where you put in your rod height. Be careful on the forums... while some understand what you mean by accurate elevations, some will say the rtk gives great positioning, but this is the position of the aircraft, NOT the focal point of the camera. Until the rtk or ppk positions for that matter are for the focal point (which changes in relation to the aircraft based on angle of gimbal and aperture setting) you are still required to set GCP's.
 
Let me also add... I have flown sites in 20mph winds with my phantom 4 pro. For about two acres I take about 100 nadir (top down photographs) using ground station pro. I like this because it will hover for capture allowing aperture priority to the smallest aperture (highest f stop possible). Based on the photon linear theory of light this is best setting for crisp images. Then I take about 150 oblique photographs using autopilot. This program does not have a hover for capture option so I have to set shutter priority to 1/1000 of a second, which in good lighting results I about f7 aperture with ISO at 200. This means at 3.7 mph the shutter is open for 0.005 feet. Which allows appropriate tolerances and good results for surveying. I am working with the dji autopilot folks to have a hover for capture option added so I can take the obliques on aperture priority. Remember to set your white balance correctly otherwise your white striping will rise off of the pavement. Do NOT use the auto white balance. Good luck... and drone on!
 
I am a surveyor as well. I use the phantom 4 pro. I get 0.05' accuracy verified by sample cross-sections doing roadway and commercial sites with my drone. I've been thinking of an upgrade to the i2 pro with the x5s. However with the results I get from the phantom 4 pro since it has the 1" cmos sensor I don't quite know if there would be an enhancement noticeable. As for the Gps... I have yet to hear of a drone that's places the Gps coordinate at the focal point of the camera and thus the resulting data is not survey grade even with the RTK drones. It's not like a Gps antenna where you put in your rod height. Be careful on the forums... while some understand what you mean by accurate elevations, some will say the rtk gives great positioning, but this is the position of the aircraft, NOT the focal point of the camera. Until the rtk or ppk positions for that matter are for the focal point (which changes in relation to the aircraft based on angle of gimbal and aperture setting) you are still required to set GCP's.

Thanks for the reply. Have you had any trouble getting good results on windy days with the P4P? Also, how high are you flying?
 
Thanks for the reply. Have you had any trouble getting good results on windy days with the P4P? Also, how high are you flying?
I fly the nadir photographs at 130 feet resulting in 1.1 cm per pixel. Then the obliques between 70-85 feet depending on environment (power lines and trees). No trouble with winds up to 20 mph. Since she will only fly up to 30 mph I wouldn't try much higher winds.
 
I fly the nadir photographs at 130 feet resulting in 1.1 cm per pixel. Then the obliques between 70-85 feet depending on environment (power lines and trees). No trouble with winds up to 20 mph. Since she will only fly up to 30 mph I wouldn't try much higher winds.

What software are you using to process?
 
I use Drone2Map, Agisoft Photoscan Pro and 3D Survey in a similar way - havent used reality capture to date - how does that rate (apart from expensive!)
 
Reality capture creates a much more precise and dense point cloud. I've used photomodeler and photoscan pro and I find that reality capture is smoother and much (MUCH) faster. I've never used 3D survey. I have a dell precision with a 4.5 Ghz processor, 64gb 2400 ram and an 8Gb nvidia video card. It processes most projects of up to 5 million points in an hour. You can pay the $7,500 for the reality capture software or you can get a steam account and buy it on subscription for $40/month.
 

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