Entry Help

Here we give you hints and tips about performing the measurements and explain some of the data entry fields we use. Please also note our background information.

Creating a Station

To create a station first select a suitable location and make at least one GPS measurement at the station. The location should be easily recognizable as the spot to measure, so that others can find it even if their current GPS accuracy is very poor. Typical locations are survey marks, signs, tree trunks, corners of walls or fences, etc. To make it even easier for others, a station can be marked with a Geodrift sticker and/or have a log book hidden in a watertight container. In addition, having the Geodrift Station ID printed on a sticker or log book directly at the station allows anyone who sees the station and the ID to go online and look it up in our data base.

For Geocachers: in general every traditional cache is directly suitable to be used as a Geodrift station. In some cases stations to multi caches are suitable, too.

To add a new station to the Geodrift data base, the measurement made at the station can directly be entered to Geodrift. You may freely select a station ID yourself. Just pay attention that after entering the station ID, the system comes up with the entry form for a New Station. If the system comes up with the entry form for an Existing Station you need to choose a different Station ID.

Format of Coordinates

Geodrift uses the WGS84 format (World Geodetic System 1984, wikipedia). Display is in degree and minutes with decimal parts. A latitude of North 51 degree, 10 minutes and 15 seconds is shown as N51 19.25 - this display format is available with most GPS receivers so that displayed values can immediately be copied to Geodrift input masks. Many GPS devices display 3 digits behind the decimal point providing a resolution of a 1000th degree (0.001). Geodrift supports higher reolutions, so if a GPS provides more digits behind the decimal point, they can be entered.

Simple Single Measurement

Place or hold your GPS receiver as close as possible to the point that should be measured. Select a display mode that shows you the most information about the received signals. Typically the received satellites are displayed graphically. Besides the coordinates one often gets information about the altitude and the accuracy or statistical accuracy.

Take a note of the name of the station, date and time, the coordinates and the elevation. It would be nice to note additional information like the numbe rof satellites received and the displayed accuracy. Unfortunately there is no standardited term for this value, so there could be other names for it, like Garmin's EPE (Estimate of Position Error).

Advanced Measurements

Many GPS receivers today have options to make more accurate measurements. For example, measurements can be accumulated and averaged over time. If displayed graphically, one typically gets measurements like shown in the picture on the right. Overall, one receives an average value that becomes more accurate the longer the measurement is taken. Our input mask currently supports average measurements taken over up to 5 minutes, up to 10 minutes, up to 20 miuntes ot more than 20 minutes.

In additon, several GPS devices support differntial GPS. Here differntial correction data collected by reference stations is received and used to calculate a more accurate position. Most often implemented is the support of receiving correction data by additional SBAS satellites (Satellite Based Augmentation System, WAAS in North America, EGNOS in Europe). GPS receiver that are capable of processing WAAS/EGNOS signals tyoically also have a display if the correction signal is currently received or not.

Highe-end devices can receivecorrection data also via radio signals or via the Internet. There are multiple commercial providers for GPS correction data. Sometimes universities or research institutes providecorrection data of their own, local reference station at no cost.

Utilities 

Using this Excel File one can enter and store measurements made in the field. The file can be directly used by Windows Mobile PDAs with Pocket Excel.

For field notes or logs, check the printer templates at www.gpssports.org.