The light weight dual frequency on board GNSS system for sUAVs was first conceptualized in September 2011 when we were once again frustrated by the lack of vision of proprietary VTOL UAS manufacturers whom we could not convince of the advantages of on board dual frequency GNSS in sUAS mapping applications. Hence we decided to take the development of this cost saving feature in our own hands and built a universal, affordable, hot-exchangeable, dual frequency GNSS V-Map (shown above on a modified Steadidrone) receiver weighing less than 130g (antenna mounting and cables included) and running at 20Hz.
Shown below in photos dating back to 2012 the platform independent V-Map system is mounted on the Aibot X6 copter from Aibotix GmbH and on an md4-1000 from Microdrones GmbH. It can be mounted on fixed wing platforms as well.
Use the V-map system
• in the air for GNSS supported SfM mapping,
• as a spatial reference back-bone in hydrographic surveying
• as well as in conventional terrestrial kinematic base-rover surveying as shown below
The V-Map system professionalizes small, modern, geo-spatial sensor platforms such as UAVs, remotely controlled autonomous boats and land vehicles. It empowers small mapping operations all over the world to make maps and geo-spatial products of professional quality. Equipped with an accurate event marker the V-Map system produces high precision camera exposure positions on dynamic platforms. The standard 1PPS port provides precision time tagging for hybrid surveying and data fusion applications. Additional ports for streaming RTCM and NMEA sentences can be furnished on request.
The V-Map concept: AFFORDABLE PROFESSIONAL SOLUTIONS through
• FLEXIBILITY
• RELIABILITY
• EASE OF USE
• HIGH PRECISION
Contact the V-team for more details
Comments
In full spirit of DIY I think that users should be informed that the same or almost the same is achievable without buying a expensive V-map system.
Ardupilot records Raw data form any Ublox gps capable to do so (like the M8T), this raw data can be postprocessed to achieve cm accuracy ( we get about 4 to 10cm horizontal) using a freely available RTKlib software tool.
For airborne receivers, having a dual frequency L1/L2 has no major advantage in accuracy if the base length form the receiver and the base station is less than 10km. So if your Plane/copter is not flying more than 10km of your gps basestation.. you will get almost the same result of an L1/L2 receiver.
Almost all UBlox raw receivers have an input timing pin that can be used to get a time synchronised message. This will allow the user to get precise time tagged pictures. Shutter delay time information can be used during post processing using mission planner. https://github.com/diydrones/ardupilot/issues/2289
Furthermore Ublox M8T is capable to provide data up to 18Hz in single mode, or 10Hz in concurrent GPS mode. this equates to a position fix every 27cm ( at 18Hz) or 50cm (at 10Hz) assuming your flight speed is 5m/s. Is also possible to perform post processing interpolation between GPS fix messages and shutter time.
Again in full spirit DIY... If L1 is not enough for you, you can achieve the same performance of the V-MAP system using a Ashtech MB100 receiver board and a Helix active antenna form Maxtena. The MB100 is about $3K and the Antenna is $400.. and remember you will need 2 of each, if you don't have already your L1/L2 base station.
Also you need to get an interface board for the MB100 ( here is something I made for a past project ).
Sure it's not as easy as buying a V-MAP System... but this is a DIY site ;)
Thanks for the comments and questions.
The V-Map system enables you to very precisely determine positions along a trajectory at a rate of one position every 0.05 seconds. So if your ground speed is 5m/s then you will get a position every 0.05 x 5 = 0.25m = 25cm along the path that your drone has flown. Using the V-Map system the coordinates of these trajectory points are accurate to the order of a few centimeters. Connecting the V-Map receiver to a camera which has been configured to generate a pulse at the exact moment of exposure allows the V-Map system to record very precisely the exact time of the exposure, a process generally referred to as event marking. This time can then be used to interpolate the exact position of the camera at the moment of the exposure between the nearest two consecutive trajectory points. The images below illustrate the spatial relationship between measured trajectory points (yellow) and interpolated camera exposure positions (camera icons).
This same principle could of course also be applied by using the common GPS receivers employed by the drone for navigation. But the type of receivers used for navigation typically run at 5Hz - i.e. giving you a position only every 1 meter at a ground speed of 5m/s. Furthermore, the common navigation GPS receiver does not have the ability to record very fine phase measurements on two frequencies. It can determine positions to an accuracy of 2 to 5m, good enough for navigational and payload control, but not really good enough for precise georeferencing in Structure from Motion (SfM) mapping. Hence the need for the V-Map system which can perform phase measurements on two frequencies of the satellite signals. In fact the latest version of the V-Map system tracks both the American GPS as well as the Russian GLONASS satellites.
The V-Map system is basically a blind passenger. It only needs a power supply of 5 to 32V from the drone. By design it is isolated from all flight management, there is absolutely no integration with the drone electronics, thus making it truly platform independent. It is typically connected to the flash hotshoe of the camera from where it receives pulses for which it records very precisely the time of the pulse. Note also that the camera is not triggered by the V-Map system. That task is typically performed by an independent intervalometer or by the autopilot.
The reason for using the V-Map system is to reduce dependence on ground control points in SfM mapping. Precise camera exposure positions (obtained as described above) can reduce or potentially replace altogether the need for ground control points (GCP), thereby significantly reducing costs in SfM mapping. To what extend the reduction or elimination of GCPs is implemented is up to the user. Not much has been written on this aspect yet. We have performed various experiments and found the results to be astonishingly good. See our White Paper here. A similar paper can be found here.
Although it can be configured at special request to operate in real time kinematic (RTK) mode, the standard V-Map system relies on Post-Processed Kinematic (PPK) mode which utilizes the same algorithm as RTK but has the added advantage of not relying on a life data link between reference station and drone and allows you to process chronologically forwards as well as backwards - thereby reducing any periods of float solutions significantly. Being experienced surveyors we felt that the extra logistic burdens and costs for providing and maintaining another radio link to the drone were not justified.
We are willing to share sample data for third party validation of our findings. Please contact us here.
For those of you who felt slighted by the lack of "sharing" on a DIY forum, please consider that while we are admittedly not sharing what is in our boxes, we are sharing very valuable information about the method which can be used to significantly improve your competitiveness in the preparation of accurate geo-spatial products by means of small drones and SfM algorythms. We are very confident that it will soon be common practice to use airborne camera positioning to reduce dependence on GCPs.
+1 +1 +1
I saw these guys at the ASPRS sUAS conference in Reno last month. It actually connects directly to the camera and records the moment the picture is taken. Pretty slick. The stupidest annoyance with Pixhawks is that issue of geotagging, which this solves. However it's a dual band gps so it's not cheap. Post processing gives it cm accuracy though.
+1 what is the purpose of this and how does it work ? I can guess this is a kind of super GPS system giving more precise position measurements versus a standard GPS. If so, this is not at all solving the issue of synchronizing the pictures with the GPS recorded positions...
I think you should explain better what it does, and why it's so useful, sentences such as "in the air for GNSS supported SfM mapping" are probably explicit for experts in the field, but not so much for the rest of us.
Maybe a video showing the thing doing what it's supposed to do would be a good help.
good to see that DIY drones is becoming more and more an advertising site for companies. Next thing we will start publishing also alibaba ads. This product has been already posted on here before, so if the V-team is not sharing anything with the community then use an advertising site not DIYdrones.