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My question intends to find out how maps are downloaded/buffered at Ground Control Station's for UAV operations. I understand GPS transmitters relay the exact location of an aircraft on a map. However, the map needs to be loaded/buffered in real time as the UAV covers ground.

For a UAV as large as the RQ-4 Global Hawk, with a range of 14000 kms, how is the map loaded in real time?

On the other hand, for amateur or small scale UAVs/MAVs, is the map updated in real time as the aircraft/rotorcraft covers more ground? Or is that the map is downloaded pre-flight, based on the range of the aircraft? This would be preferable in terrains with poor or no signal connectivity.

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  • $\begingroup$ Isn't it more likely that a military system like the RQ-4 ground station would have pre-loaded map data, like a $50 satnav does? I'm sure the costs are trivial compared to the price of an RQ 4. They also probably need it in advance for mission planning and rehearsal. $\endgroup$ – RedGrittyBrick Sep 10 '14 at 10:13
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    $\begingroup$ for military uavs, range should be interpreted as time on station, where the aircraft loiters around a particular area for a length of time. unmanned aircraft are rarely (if at all) flown from one base to another over such a distance; there's too many unknowns to raise the risk level for such a mission. typically, they're disassembled for transport and reassembled in theater. $\endgroup$ – Erich Jan 27 '15 at 3:56
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For an application that were controlling a hobbyist UAV one could use something like the Google Maps API. It provides services and data that will scale as the user scrolls in and out and as the UAV transitions to different areas. It also has the advantage of having visual and road data as an option. The downside is that unless you download enough data ahead of time you must have some sort of data connection to the application. But, with the greater availability of the fast cell based data connections this is becoming less of an issue.

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You seem to assume the maps are being transmitted from the UAV.
They are almost certainly not (and if they are that's a poorly engineered system and I would be embarrassed that my government wasted my tax dollars on such a lousy design).

Maps are relatively static data, so it would be logical to store them on the computers at the ground control station (where you could have the entire world's terrain and likely aeronautical charts/airspace boundaries on your hard drive, along with current weather data and other useful information).

Moving the map to keep up with the position being relayed from the UAV is computationally trivial: iPads do it for real aircraft (ForeFlight & similar products) and your car's GPS system does it when you drive - neither system is as powerful as the typical desktop computer.

All the UAV would relay to the ground station is its position (and any other pertinent data dictated by its mission, such as photos/video). This arrangement minimizes the bandwidth required to control the vehicle, as well as its RF signature (less stuff to transmit back to base).


For autonomous UAVs, particularly ones which have to avoid airspace incursions, some subset of airspace data appropriate to the route of flight may be loaded on the vehicle, but I wouldn't call these "maps" - it's a much more compact representation of coordinates marking boundaries in 3D space (similar to the Jeppesen NavData products - possibly even using those products) . Such vehicles may also have terrain data loaded before flight if they lack other means to avoid collisions with terrain while operating autonomously.

Disclaimer: I have no experience with the RQ4 or any other military UAVs - this is just a common-sense engineering assessment.

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  • $\begingroup$ Thanks for the answer, however, i'd like to clarify that i did not assume the maps are transmitted from the UAV. That would indeed be a very poor work of engineering. I feel that for hobby/small scale UAVs, it would be cumbersome to keep large maps of different zoom values stored beforehand. And yes, moving a map to keep up with the UAV is no biggie :) $\endgroup$ – Pranav Sep 9 '14 at 16:31
  • $\begingroup$ @Pranav I suppose it depends on how many zoom levels you need, for example most aviation apps provide 3 levels of zoom for VFR charts (which are actually three separate maps: WAC, Sectional, and TAC). It's not too difficult to pick which chart to show based on the current zoom level. For short-range UAVs you wouldn't need as extensive a map collection and one high-res georeferenced map would probably be good enough. $\endgroup$ – voretaq7 Sep 9 '14 at 16:57
  • $\begingroup$ Indeed, for short range UAVs, the map requirements wouldn't be too large. One more thing, though this might be an extension to the question, how are maps usually downloaded for small scale UAVs? $\endgroup$ – Pranav Sep 9 '14 at 17:10
  • $\begingroup$ I don't even think "maps" would have to be downloaded to the UAV. Using common sense engineering, you would just provide a start point and end point. A UAV could then just circle the area for a predetermined amount of time and then return. It doesn't need maps. If it was remotely controlled, it still wouldn't need maps either. The UAV just needs to report it's position and the ground station can just display it on a map. I have no experience with UAVs so this is just an educated guess. $\endgroup$ – Brian Sep 9 '14 at 20:25
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    $\begingroup$ @Pranav: Having used several of the open source hobbyist UAV hardware myself I can say that at least for hobbyist UAVs you don't upload maps to the UAV you just upload waypoints - a list of coordinates the UAV is supposed to fly to. $\endgroup$ – slebetman Sep 10 '14 at 4:03
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Military UAV's have a library of maps (on a hard drive associated with the ground control station) that the pilot chooses from while flying. Formal flying charts are loaded underneath a 'moving map' display. The pilot can select a wide variety of charts from a small scale GNC to a large scale VFR chart.

There is a limit to the buffering obviously, and if the aircraft flies outside of the buffer than the pilot just manually loads a new map for the new area.

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    $\begingroup$ generally speaking, a military uas pilot will have all the maps required for his area of responsibility, loaded during preflight as mission requires. manually loading maps during mission would be a very rare event, as it would mean an extreme deviation from an otherwise normal mission. from my experience, we had map data in the system for areas well outside our general aor. so if you are flying in the centcom aor (already really huge), you will generally have all that map data available already. flying outside that area gets geopolitical real fast. $\endgroup$ – Erich Jan 27 '15 at 3:17
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Amatorial drones: normally these boards have flash memory as not-mandatory, everything has to be loaded in to RAM or on limited space on-board. Also communication between UAV and GCS is not mandatory.

Most complete (open) GCS + software seems to be ArduPilot, and its trick is that the map is only PC-based; you set your travel point (waypoint) on GCS, connect the UAV by cable if no wireless link is present, upload the waypoint GPS coordinates, and let the mission begin. If you have a wireless link you can obviously load or edit waypoint on-the-fly.

Now think about this: how a map should be helpful to a drone? Because he may recalculate the route on its own. But why should it do so? Drones normally are "blind" to environment, and radar/lidar/vision items are complex, expensive or require a lot of computing power and space on the drone. In that case adding a microSD with the map in full precision of the region you are gonna fly is not a problem (OpenStreetMap planet map is about 40GB), but again I assume the pathing algorithm would just override the waypoint setting every time a course correction is needed, and another specialized algorithm would kick in to avoid low-term collision, which ignores completely the route.

Please note that many drones have a "return to home" function, that when the link is lost and mission complete, the drone heads directly to home. And as many amatorial drones are blind, that may have unexpected results.

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