When the instrument is appraised, the formula for calculating the ranging error is (2+ 1ppm).

What is the relationship between the two?

The concept of 1 mm +2ppm

1mm+2ppm is the abbreviation of 1mm+2ppm×D (km), which reflects the nominal ranging accuracy of total station or range finder. These include:

1mm represents the fixed error of the instrument, which is mainly caused by the measurement error, centering error and phase measurement error of the instrument plus constant, and the fixed error has nothing to do with the measured distance. That is to say, no matter how far the distance is actually measured, there will be a total station fixed error not greater than this value.

2ppm×D km represents proportional error, where 2 is proportional error coefficient, which is mainly caused by instrument frequency error and atmospheric refractive index error. Ppm stands for one millionth (several), and D is the distance actually measured by total station or range finder in kilometers. With the change of the actual measuring distance, the proportional error of the instrument also changes in proportion. For example, when the distance is 1km, the proportional error is 2mm.

For the total station or rangefinder with ranging accuracy of 1mm+2ppm, when the measuring distance is 1km, the ranging accuracy of the instrument is 1mm+2ppm× 1km = 3mm, that is to say, the total station ranging is 1km, and the maximum ranging error is less than 3mm.

In particular, it is pointed out that the nominal ranging accuracy is a concept of error limit, that is, the ranging error of each total station or range finder should not exceed the nominal accuracy provided by the manufacturer.

Different total stations have different instrument constants. This constant was entered when you purchased the instrument. There are instrument constants in the manual. You can look for it in the manual attached to the total station, but in fact the accuracy of the instrument will be higher than that in the manual. Accuracy can't be changed casually. If you are not sure, you'd better take it to the instrument store for inspection.

Of course, if you have the conditions, you can find it by the following methods (theoretical methods):

1. Set multiple points at different intervals on a straight line.

2. First, observe the distance between the first point and the second point.

3. Then observe the distance between two points in each paragraph.

The sum of each distance should be the whole length of a straight line.

5. When the whole line directly observes the distance, it contains only one additive constant, and each observation contains one additive constant. So,,, and should count?

As for the prism constant, it is better to know. At present, the domestic prism is generally -30mm, and the imported prism constant is 0mm Nikon +30. How to judge is simple:

1, draw two points on the ground with a distance of three meters.

2. Put a total station at one point and a prism at the other.

3, prism constant input -30mm, if the measured horizontal distance is 3m, then the prism constant is -30mm, and the actual distance difference between 3 m is the prism constant! This method was taught by an old master and has always been very useful! !