Recently this product was presented at the ESRI User Conference in Spain, just last week and this next will be in the TopCart in Madrid.
It is a GPS positioning and measurement system that supports post-processing, with which centimetric accuracies can be obtained. Nothing that other systems do not do, but what has caught our attention is the price.
How it works
Basically, the device works like a logger. It is connected to a magnetic external antenna and captures raw measurements of distance to the satellites in files that are then downloaded via USB to the computer. It supports data from points, routes and polygons, for the latter it calculates areas.
It has the size of an iPod, very light, such that it can be carried in a pocket or even placed with Velcro in the cap that comes included, so you can easily perform moving measurements with hands free.
The difference of this, with a traditional logger, like the one used by the traced vehicles (black box), is that they record the raw measures with which they can later be post-processed.
Similarly, browser-type GPS only captures positions, with accuracy between 3 and 5 meters but that can not be improved.
The data that is downloaded to the computer are the files that contain raw measurements of distance to the satellites (pseudorange and carrier phase), apart from standard NMEA messages. Even without post-processing, the accuracy of the NMEA is better than that of a standard navigator-type GPS, given that the external antenna significantly decreases measurement noise.
What details can be obtained
Additionally, Posify offers a post-processing service, since the captured information is sent and returned already processed in differential mode with respect to the nearest GPS reference stations.
The precisions that can be reached are:
- 20 to 30 centimeters for moving measurements
- 2 to 3 centimeters for static measurements
The vertical precision is from 2 to 3 times the horizontal precision.
The data comes in kml and shapefile format. Additionally, the information related to the postprocess, in the case of the points of one kml, each one keeps information such as its latitude, longitude in formats degrees / minutes / seconds and in decimals. Also the ellipsoidal and orthometric altitude, coordinate UTM, number of visible satellites and estimated accuracy after the postprocess.
How much is Posify?
Posify costs 326 Euros, plus taxes, in total close to 395 Euros. This includes:
- The Posify logger. This brings a micro SD card of 4 GB, which can store up to 1,300 hours of uncompressed recording.
The internal lithium battery supports up to 12 hours of use and is charged at 4 hours ..
The GPS obtains data in L1 frequency up to 50 channels, with binary UBX / NMEA code and format every second.
- An external magnetic antenna with 1.50 meter cable, SMA connection.
- A metal base plate for the antenna, with 10 cm. diameter.
- One USB / micro-USB cable
- An "Army" cap with velcro to carry the antenna and additional velcro
It does not include the USB charger, because for that you can use a charger any of which we sure have several left over for each mobile device we have bought.
For the post-processing, 99 Euros per year is paid. The first year is free, as it is included with the purchase of the equipment.
That is not Posify
It is understandable that the device is a data receiver. It does not have a screen to go browsing as it is done with conventional equipment. Although considering that now any mobile has a built-in GPS, the possibilities are interesting.
As an example it can be used to transfer information in real time to a Smartphone.
Apart from recording measurement files on the internal disk, the Posify logger provides real-time information about the satellites through the USB port. This information (data) includes the code and phase measurements, and also the NMEA messages from the standard GPS solution. The USB data (measurements and NMEA messages) are generated with the same cadence as the recording of files (every second). The USB data is generated permanently regardless of whether the logger is recording a measurement session or not. That is, as soon as the logger is on, the USB port generates output constantly.
This has several possible applications, connecting the logger to a laptop or a mobile terminal (PDA, smartphone):
- Visualization of the status of the GPS constellation on the screen (from NMEA messages)
- Recording measurements continuously in a computer (reference station)
- Real-time positioning (Real Time Kinematics or RTK)
The figure shows the display of GPS satellites in real time on a smartphone. The application gives information about the number of satellites in view, their azimuth and elevation, and the strength of their signal. It is also interesting to look at the DOP (Dilution Of Precision), which is a value that indicates the geometry of the GPS constellation: the lower the DOP the more favorable is the geometry of the satellites for positioning accuracy.
Where is it available?
Currently only for Spain. It works with near 180 reference GPS stations spread over a large part of mainland Spain. The network includes the stations of the National Geographic Institute (IGN) and those of most of the Autonomous Communities
Posify works directly in the official Spanish system ETRS89, in several formats of latitude / longitude. In height, the ellipsoidal value (ellipsoid GRS80) and the orthometric or sea level value (EGM08-REDNAP official geoid)
It seems to me an interesting product, which we will have to follow because surely we will know more about them.