Safari: Geodätische Punkte

This is a virtual Safari-Cache. It is not tied to a fixed location but can be solved in different locations. The coordinates given above are for example purposes only.
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Geodetic reference points

Geodetic measuring points have been around since the 19th century: they serve as fixed reference points for surveyors. These points are differentiated into position, height or gravity fixed points.

In Germany there is one fixed position point for every 1 - 5 sq km, whose coordinates and height (accurate to approx. 5 mm) can be used as a reference point. Sometimes these are inconspicuous granite blocks, indentations in rocks, embedded metal plates and much more.

The height reference points are reference points for height information and measurements. You have the right to specify the height to the nearest 1 mm. The position control points do not meet this level of accuracy. Height fixed points require that they be attached to a particularly stable surface. They are often found as metal bolts on church towers, buildings or rocks.

Gravity fixed points serve as reference points for gravity. Since the Earth is a very irregularly shaped structure, the force of gravity or the local gravitational field varies depending on the position on the Earth. This in turn means that the vertical direction can differ in different places - vertical is not the same vertical everywhere. Since surveyors use devices with spirit levels, they must take gravity variations into account if they are to be accurate. There are around 16,000 such gravity points in Germany.

In general, the above fixed points are often very inconspicuous, sometimes even underground. Lists of where such fixed points are located can be purchased from surveying offices or discovered in the 1:25,000 topographic maps. 'Public' fixed points, on the other hand, are rarely found.

The European Terrestrial Reference System 1989 refers to the stable European continental plate. This means that the ETRS89 coordinates remain permanently the same. This reference system is suitable for precise satellite measurements in the centimeter range.

This is how easy it is to check your GPS device:

Set your GPS device to the WGS84 reference system and the coordinate system to Geographic or UTM. Place your GPS device on the geodetic reference point and have the coordinates determined. Compare your measured coordinates with the coordinates of the reference point.

To the cache

The log conditions are quite simple, depending on what your 'Geodesic Point' looks like:

• If no coordinates are noted on the geodetic point (as in the adjacent image), photograph the part with a GPS device in the image; GPS information in the EXIF ​​data is not saved on Opencaching! Be sure to enter the coordinates in the log.
• A picture of the surrounding area must also be uploaded.
• If coordinates are noted on the geodetic point, take a photo of the part with recognizable coordinates and a personal object or yourself.
• Only one log is permitted per geodetic point (the exception is a team log), it is first come, first served!

The geodetic point that inspired me to do this is on 'La Gomera', the second smallest of the Canary Islands, above the Valle Gran Rey on the 'summit' of La Merica. Coordinates are not noted on it, they are:

N 28 06.895 W 017 20.194