GPS and Data Collection

What is  GPS

The Global Positioning System (GPS) is a satellite-based navigation system which provides exact position on the Earth anytime, anywhere, in any weather. A network of 24 satellites is orbiting in space and transmits signals that can be detected by anyone with a GPS receiver. With distance measurements from four satellites, the position on the earth is determined. Launched by the U.S. Military in February 1978, The GPS technology has tremendous amount of applications such as navigation, mapping and GIS data capture.

How GPS works?

The principle behind GPS is the measurement of distance between the receiver and the satellites.

GPS satellites are orbiting in space 20 000 kilometers from Earth. The satellites are constantly moving, making two complete orbits around the Earth every 24 hours. Each satellite transmits radio signals that allow a GPS receiver to estimate the satellite location and distance between the satellite and the receiver. The receiver uses the measurements to calculate where on or above the Earth the user is located. With a minimum of three or more satellites, the GPS receiver can determine a latitude/longitude position. With four or more satellites, a GPS receiver can determine a 3D position which includes latitude, longitude, and altitude. By continuously updating your position, a GPS receiver can also provide data on your speed and direction of travel.

Recent Advancement in GPS Data Collection

Recent advances in Global Positioning System (GPS) and mobile technology facilitates rapid field data collection and transfer. With the introduction of Palm Pilots followed by pocket PC operating system, a new generation of handheld Personal Digital Assistants (PDA) has flooded the market. These handheld devices can be used with GPS receivers to collect information in the field. Once the location and attribute data have been collected, all the data can be imported in Geographical Information Systems (GIS) for mapping and analysis.

In addition, new mobile devices such as Tablet PC or smart phones can be GPS equipped and offer a larger choice of solutions for field data collection. New Tablet PC are now available in ruggedized versions and can be used for mapping applications in outdoor environment. Next generation mobile phones currently entering the market provide users with wireless Internet access and allow them to transmit real-time Minformation on their precise location. With the avaibility of smart phones, new services are offered such as location-based services (LBS). In these applications geographic data and processing are provided as a type of service over a wireless network connection.

Palm-Sized Pc GPS Data Collection

GPS can be connected to palm-sized PC such as Pocket PC or PalmPilot in order to operate field surveys. The system consists in entering data with forms and the location is automatically saved with the GPS. During the field survey, it is possible to collect spatial and attribute data. The recording format is a standard GIS data format and makes easier the data transfer to a database. The advantage of this solution is to reduce the risk of error in data entry and thus improve data quality and information is immediately available in a GIS data format. A mobile device such as a palm-sized PC is not limited in capturing GPS points and it is the other interest of this tool. In some cases, positional accuracy can be improved with differential GPS. In opposition with a simple GPS receiver, this solution comes with adata logger software. ESRI’s ArcPad software is described in the following guidelines but other softwares are available and some of them are free on PalmPilot.