# Question About flight altitude for mapping

Hi Folks.

I am a long time, experienced user of drone deploy and mapping with the app. Nevertheless, I came upon a situation I had not come up yet. I need to map an area of land that lies from to topmost part of a hill chain towards the valley. The highest peak of these mountains are 250 meters above the lowest.

As I have always done before, I plan on setting the starting point for the flight so that I am taking off from the highest point in my flight plan, which will already be 250 mts above most of the rest of the area to map. So I figure that setting a mission flight altitude of 50 mts would be perfect since that height enables me to fly almost most of the mission 300 meters above most ground level.

The problem is that the area to scout is 200 hectares, so if I set the flight altitude to 50 meters and take off from the highest point, Drone Deploy thinks I will only be flying 50 meters above ground level and gives me a 409 minute, 29 battery flight plan.

On the other hand, if I take off from the lowest point and set a flying altitude of 300 mts, DD gives me a 38 minute Flight Plan on 2 batteries.

Is there a way to tell the app the set mission flight altitude is AGL and not ATO??

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Have you tried terrain awareness? That is allot of elevation change so you might need to do more of a facade inspection type flight. Then you could stay 250-300ft AGL.

I am not that interested in having a super accurate rendering of the walls of the hills, to put it in some way; I do need as much resolution and detail in the rest of the valley downwards.

This map is for studying rainfall flow coming from the hills into the valley.

So technically, what I need and can not make the program understand is that once the drone takes off, it will be flying 90% of the time at 250-300 meters AGL and not the scarce 50 meters AGL it has on take off point. The drone wrongly assumes that the whole mission will have it flying those 50 meters ATO (above Take Off), and thus generates a very dense grid for the flight pattern (it takes like two zillion batteries to complete and 4 hours); I need it to understand it will only be 50 meters at one side of the flight pattern, when it comes back over the hillsâ€™ ridge, so it generates a grid that concurs with the â€śrealâ€ť AGL.

I have not flown before with the Terrain Awareness feature; itâ€™s been a while since my last mapping, it is new for me. I assume it works by making the drone increase itâ€™s stated mission altitude in response to rising terrain on the flight map? Anyway, I tried to activate it for the mission plan, but it does not seem to be available unless your mission height is over something like 150 metersâ€¦ so itâ€™s back to the starting problemâ€¦ unless I am reading the feature the wrong way, and setting a 150m height means the drone (or software) will keep the drone at a constant 150m AGL, responding the changes in the terrainâ€™s height???

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I am almost certain that as long as the area you are in has cellular coverage a reference surface available that TA is going to do exactly what you need it to but I am not clear on what the 150m you are referencing is. Can you post a screenshot of what you are seeing?

Basically TA allows a SRTM (Shuttle Radar Topography Mission) surface to be loaded in the background that will allow the drone to fly at a consistent AGL (not elevation) so that all the imagery has a consistent GSD (Ground Sampling Distance). This greatly increases accuracy but more importantly maintains resolution in low-lying areas. These are typically get worse because you have to maintain that AGL from the high point without TA.

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Sorry I am not seeing a reference to 150m but you are over the 200 acre limit. It is limited because of the number of waypoints that DJI allows to be held in the drone. Make a copy, break it in halves and see what happens. Make sure to hit the toggle.

Yeah, wellâ€¦ Back to the start.

The number of waypoints on the mission are due to the fact that the software thinks the drone will be flying 50mts AGL and not 250â€¦ one way or the other, I get back to the same issue.

I think Iâ€™ll just fly from the lowest point and make the mission altitude 250mt and get done with it already

With TA the number of waypoints increase because it has to add a waypoint to each grade break in the surface. The more undulating the surface is the more waypoints that will be created. A limit also appeared in the last year or so because of precision point return and creating additional waypoint along the lane.

Without TA you need to take of from the mean elevation.