As of Map Pilot version 2.0.0 it is possible to areas that are higher or lower than the takeoff point to facilitate accurate overlap calculation for varying terrain.
This image shows that a ground offset of 20.3 meters has been selected with the standard 75/75 overlap setting. This will make it so that the 75/75 overlap will be calculated for a plane that is 20.3 meters higher than the takeoff point. This will add 20.3 meters to the flight altitude selected in the Altitude/GSD slider panel.
This is especially useful when you are trying to map a roof, treetop canopy, hill or valley where the it would have been difficult to get proper overlap without this setting.
It is possible to adjust the ground offset up to 50% of the selected flight altitude.
"This will make it so that the 75/75 overlap will be calculated for a plane that is 20.3 meters higher than the takeoff point."
I'm seeking to understand the effects of adjusting Offset. The comment from above implies that the mission configuration changes based upon the setting. Yet it does not appears to change the path, images, etc. in the way that Overlap changes them. What are the effects of (and reason to) changing Offset? I create aerials over 150' trees and am very interested in this function. Thanks in advance.
The ground offset feature is designed to get the designated overlap on an area that is at a different elevation than the takeoff point. Imagine you want to get 70% overlap for the roof of a building that is 20 meters tall and you want to take off from the ground. Before you would have had to guess at how much higher you would need to put the overlap setting to get that value up there. Now you can use all of the normal controls for overlap and desired GSD/altitude and put in that ground offset to take care of the rest. Basically it just slides the exact flight plan that is shown up and down in altitude.
Will setting a ground offset have any impact on the drone's altitude itself?
I am very interested in an answer to the above question, while playing with offset i expected to see longer flight times/ more pictures ( or less depending on + offset or - offset).
With an altitude set of 80 meters and offset to 20 meters will the quad fly at 100 meters ??
All the Ground Offset feature does is move the flight plan up or down in altitude to let you optimize the overlap for a height other than the ground where you take off. All the images are taken at careful spacing to get appropriate overlap with reference to the takeoff location. If you are shooting the top of a building or tree canopy for example, you would use a +20 meter ground offset. Otherwise, your 70/70 setting is going to be more like 55/55 and not be very good.
Bert: It will not affect the number of images taken or the spacing of the passes which is why you are seeing very little change in the flight stats. If you have a positive 20 meter offset and your flight altitude is set to 80 meters it will fly 80 meters above a point that is 20 meters off the ground, or 100 m.
As of Map Pilot 2.1.6 this feature now works with the Terrain Awareness feature.
Hi Zane,
"If you have a positive 20 meter offset and your flight altitude is set to 80 meters it will fly 80 meters above a point that is 20 meters off the ground, or 100 m." Does it mean it will fly at 100m for the whole project (without Terrain Awareness)?
We want to map a mountain area with 150m at peak and want to get 10cm GSD with Phantom 4. Normally, to achieve this it will fly at 230m without Ground Offset, so if we set Ground Offset = 100m, it will fly at 330m for the whole project?
"It is possible to adjust the ground offset up to 50% of the selected flight altitude."
What is point of this limit?
If you need to have a ground offset of 70m (trees frequently grow to this height and taller in the tropics) but still want to map at high resolution (say 30 or 40m) why is this not allowed for? Best you allow is setting flight height at 67m and offset of 33m and then you are forced to mess about with overlap percentage.
You mention in a comment above that this feature "now works with Terrain Awareness". If you're successfully using Terrain Awareness to keep the GSD consistent, are there situations where you would also use an offset? That's the confusing part to me. Would it be in situations where you are mapping mostly a built-up environment, as opposed to just varied topography that would already be picked up in SRTM data? Thanks
Imagine mapping an area with 100ft tall trees everywhere. The overlap gets calculated assuming it is collecting images on the ground. The 100ft top of the tree canopy would get much less overlap than prescribed in the settings. The Ground Offset feature moves the plane for which the overlap gets calculated up to the level of interest, not necessarily the ground. The same is true for building roofs and things like that.
Thanks for the extra details, that makes sense regarding the overlap numbers remaining accurate after using offset.
Is this ok to use with the Parrot Sequoia camera, knowing that it is calibrated for MME's NDVI at 80 meters?
Garret: The 80 meters only applied when the Ninja was being used to stack the imagery. Since you are doing your own stacking at this point it won't matter.
Gotcha! Thanks!
Hi. Good information. I’d like clarity on Veha La’s , Bert, and others question please. Does adding the ground offset increase the actual flight altitude? That is if a flight is set for 30 meters and then say the ground offset is set to 10 meters, will the flight be flown 40 m? Is that correct? Or will it be still be flown at 30 meters? Some of the comments are years old but still critical to understand actual altitude to be flown of course. Thank you.
This will add or subtract whatever value is selected to the flight altitude selected in the Altitude/GSD slider panel.
Hi Zane,
it´s really quite confusing.
Here above you are stating that the offset value is added to the preselected height (so the 40 m instead of the 30 m like one post above).
But in your video - Map Pilot Pro - Mission Parameters Basics Part 2 - https://www.youtube.com/watch?v=HzniF98vT0M - it´s said that the PRESET HEIGHT REMAINS (e.g. 60 m from the video) FOR THE FLIGHT and ONLY THE PHOTOGRAMMETRICAL CALCULATIONS ARE ADAPTED for the desired overlap and the 40 m height resulting with the offset!?
So what is true?
Will the preset height (desired or necessary flight height) been altered with the offset value or is it only a virtual calculation thing?
What relly matters for security in the end is the real flown height!
Thanks and best regards!
Steffen