Map location discrepancies
I have made an interesting observation regarding the locations of the centres of various mission components in a flight plan.
On my desktop, I have prepared a 'close-up' survey of an archaeological feature and then sought to make small changes to it on my phone, which are likely to be required in the field due to the small tolerances of distance, centre of interest etc.
What I have noticed is that there is a difference between the desktop and mobile app locations of the centres of all the mission components that amounts to about a meter. I appreciate that the various parameters involved in a mission have a tolerance in flight due to a host of reasons, but one would still expect the presentation during planning to show the various components as being in exactly the same place, whatever device is being used to plan.
The first grab shows the centre of an orbit component number 5 to the right of a bend in a wall.
The next grab shows the same orbit centre located on the bend of the wall on the phone app instead of a bit to the right as in the first grab. So wherever I place the centre of the orbit on the desktop, the change immediately appears on the mobile app, but shifted over a little. The converse applies if I make a change on the mobile that then appears on the desktop in a slightly different location. The same applies to all the components.
While this difference is not going to make too much difference to my actual survey, I am curious to know why there is a difference at all and if it is due to some different reference data being used by the desktop and mobile app regarding maps.
Am I right in assuming that the plan on my phone is the one that the drone will be based on, rather than the desktop version?
I would be interested to hear your thoughts.
Regards,
Julian
Comments
5 comments
Those appear to be different base layers. Are you using Mapbox for both or did you switch to Here for the web?
Having just checked, the top grab (desktop) is HERE and the bottom one is MAPBOX. Having now set them both the same (to HERE satellite) the discrepancy has gone. However, that leaves the question of which map is the more accurate one in terms of actual location. The HERE one?
Julian Perry, I think this maybe a case of using georectification out in the field, more details here
https://support.dronelink.com/hc/en-us/articles/4416141457171-How-to-Enable-Drone-Offsets-Mission-Alignment-Georectification
Thanks for that, but isn't this option for a higher level package than my 'Enterprise'? If I knew which of the map options was a better match with the actual landscape then I presumably I wouldn't need georectification.
Geo-rectification also corrects for the error in the drone’s GPS signal in addition to the map base layer. It is impossible to say which base layer is better because it really depends on the location and there is no way for us to know without ground truthing it by geo-rectification.
Please sign in to leave a comment.