Smart phones, tablets, and GPS Positioning Accuracy

To meet the needs of all business personnel and make full use of your ArcGIS platform resources, at the same time, it is very difficult to design a mobile solution that can be efficiently used on popular mobile device platforms.

Location is very important. It may make or destroy a GIS application, depending on the plotting function you want to do. When you are thinking about a smartphone or tablet application, one of the first problems to be clarified is: How accurate is GPS? The answer may increase the requirements when you select a device platform.

Smartphones and tablets that enable cellular networks usually contain an integrated GPS chip, which is generally made by companies like Qualcomm, Broadcom, or CSR. The primary consideration for these chips is power consumption, positioning and Calibration Time, and positioning accuracy. In our tests, we found that about 90% of all points in the sky were within three meters of the baseline. These results are not too bad!

When we encounter a severe multi-channel interference from the receiver, the result is even worse.

Most chips also support the global navigation satellite system, that is, they support both the us gps satellite and the Russian GLONASS satellite. In this way, you will receive better satellite constellation support in the field.

Next we will connect the smartphone to the external GPS receiver, which is a real consumer-level product. The first consideration for the design of these chips is positioning accuracy, followed by positioning time, followed by power consumption. We found that there are a variety of receivers available for you to purchase, including direct connection to devices or Bluetooth connections, and most of them have SBAS (regional wide area differential enhancement system) features! In the open sky, almost 99% points are within the 3-meter precision range, and about 70% points are within the 1-meter precision range! As expected, positioning accuracy will decrease in blocked environments, but overall (much better than built-in GPS chips.

Finally, we connected an iPhone 4S to a high-precision dual-frequency ing-level receiver (from Altus positioning systems, using a commercial product GPS cable from AMAN ). GPS cable will create an external connection to almost all external GPS receivers (using RS-232) and send NMEA as a stream to the location manager on the smartphone. This replaces the positioning source with a consumer-Level External GPS device. Not to embarrass other receivers we test, but to ensure that we only use the receiver itself and not use the ntrip enhanced positioning source (although we can do this), we choose to only use SBAS, and did not fully utilize all the capabilities of the receiver. Even so, we found that almost all vertices (more than 92%) are within 1 meter !!

There are several points that need to be mentioned: the exact point positioning (PPP: precise point positioning) is becoming a reality, and you will get the centimeter-level positioning result directly from the satellite lock! This is undoubtedly a great solution for users who want high precision and do not need post-processing and cannot access the GPS network.

Therefore, before you decide to spend money on purchasing mobile devices from hardware vendors that promise sub-meter positioning accuracy, consider the business needs and the feasibility of using smart phones instead. If your business staff have not received basic high-precision GPS Positioning training, but want to use trendy mobile devices to collect data, you can set collector
The for ArcGIS application is a low-cost solution.

To view some test results, click webmap.

Address: http://blogs.esri.com/esri/arcgis/2013/07/15/smartphones-tablets-and-gps-accuracy/