This is highly precise 3D (X, Y, Z) data that is created by using the aircraft laser [LiDAR (Light Detection and Ranging)] surveying system ALS. Reflected waves from laser beams, that are transmitted out to the ground using downward-looking LiDAR instrument mounted onto an aircraft, scans the ground and this captured information is analyzed coupled with location and pose estimation information from the GPS/IMU to produce the 3D data.
The two types of data provided
■Digital Surface Model (DSM)
Using data obtained through laser, DSM is produced through the digitization of all ground surface information, including buildings, etc., at intervals of 2.5 m.
■Digital Terrain Model (DTM)
Using data obtained through laser, DTM is produced through the digitization of terrain information, excluding all structures such as buildings, at intervals of 5 m.
Data Specifications
The data is highly precise laser surveying data, with ground data precision of ±30 cm in the X/Y direction and 15cm in the Z direction.
Case Study 1
■Simulation of flood
Using 3D models, it is possible to simulate flood situations.
This allows users to see, at a glance, the flood situations that may arise as a result of heavy rain or rivers overflowing their banks.
Case Study 2
■Analysis of wave propagation (linear)
It is possible to conduct an analysis of wave propagation during microwave network planning.
As microwaves have strong linearity, it is important to get a grasp of the obstacles that lie along the propagation path.
In such instances, it would be easy to use 3D models to find out if there are any obstacles.
Case Study 3
■Detection of landslide volumes
It is possible to measure the volume of landslides by comparing the original terrain and the terrain after a landslide has occurred.
A comparison of the data at the two points in time can be applied to analyses of the volume and landslide mass of the landslide.
Case Study 4
■Snow (accumulation) survey
It is possible to conduct a survey on the extent of snow accumulation in mountainous regions and during the winter seasons. Such surveys were originally carried out using fixed-point observation, stereo photos, and satellite images. It was thus difficult to obtain accurate measurements of the snow surfaces and depth of snow deposits. However, it is now possible to conduct such surveys using aircraft laser surveying technology.
- Q1. What is ALS?
- Q2. What is DTM?
- Q3. What is DSM?
- Q4. What is the approximate level of precision?
- Q5. What are the applications?
- Q6. What is the projection method?
- Q7. What is the data unit?
- Q1.What is ALS?
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ALS, Airborne LiDAR System, is a new surveying system that makes use of aircraft laser, digital cameras, GPS, and Inertial Measurement Unit (IMU).
Using GPS and IMU, the measurement position when the laser beam is fired is computed; with regard to the digital camera, the slope at the time of photography is computed.
- Q2.What is DTM?
- DTM is the acronym for Digital Terrain Model. It refers to elevation data for ground surfaces only, excluding structures. This data is obtained from the elevation data for ground surfaces and structures, measured using laser beams fired from aircraft.
- Q3.What is DSM?
-
DSM is the acronym for Digital Surface Model. It refers to elevation data of ground surfaces and structures, measured using laser beams fired from aircraft.
This is point data with XYZ coordinates of a 2.5 m mesh.
- Q4.What is the approximate level of precision?
-
The precision of the measuring equipment is 15 cm.
However, after undergoing several processes to convert it into a product, the precision becomes approximately 20cm.
- Q5.What are the applications?
- Simulation of a flood situation, analysis of wave propagation, detection of landslide volumes, survey of snow accumulations, etc.
- Q7.What is the data unit?
- The unit used is the same as that used in the National Basic Map (2 km × 1.5 km).
