Elecrtonic Distanse Meter
The principle of EDM is based on Fizeau's method of measuring the speed of light.
It was Swedish AGA Co. that challenged this again shortly after the war 2.
I wonder why the gas companies started this.
Anyhow, when the accuracy of light speed measurement improved,
AGA developed a rangefinder(EDM) using light speed (1953 Geodimeter 1).
Sokkisha Co. has been involved in EDM research and development
by the request of universities and research instituies in 1963.
The purpose of these requests were for the geophysical observation
or standard survey(Trilateration surveying),
aiming longer distance measurement around 10km or more.
And then, we started to develop the instrument of name ERI like Geodimeter.
Unfortunately, we did not complete this misson because ,
such products were very critical and the very samall demand from the market.
So we have changed the direction to the instruments for more popular survey.
Around that time, LEDs became more popular. LEDs were the best light source
because of their smaller size, easier modulation, and lower power consumption.
However, we found that there was no modulation uniformity
on the light emitting surface and solved it.
ERI for the long distance measurement.
1.Semi totalstation SDM 3 released.
In 1971 Developed a coaxial EDM of angle's and distance's axis.
Released the first EDM model name SDM 3 in Japan.
SDM 3 consisted of an optical angle measurement unit
and an electronic distance measurement unit separately.
The angle measurement was made by conventional optical methods
2.Stand alone EDM , RED 2L
Capability of the distance measure 4km with 1 prism,
and used a CPU to adopt various functions , horizontal reduction etc.
3.Semi Totalstation SDM 3D
Semi-Totalstation with optical reading performance of 10 seconds angle.
The beauty will be the best in the world.
Since then, the competitive companies around the world have started to produce
by imitating SDM3D design concepts some what.
Indeed, the telescope section and EDM section were integrated
and telescope was rotatable 360 degree.
In addition to the keyboard, enable the remote control operation
by the infrared optical communication.
4. Red Mini
The smaller size EDM device mounted on a telescope aimed to be the smallest EDM
in the world.
This was developed from the market research results that reported the majority
of surveys were less than 300m distance or area.
Distance 300m with 1 prism
The master device that has spearheaded the digitization of surveying
along the handheld data collector.
6. NET2 (MONMOS)
Angle 1 second angle
The 3D measuring device that enables higher accuracy measurements
for the large construction structures.
It is the tip of this kind of products.
After that , the accuracy improved more and it reached to the motor
driven robotic device.