Latest Contributions by larryzhang

Introduction Airborne & terrestrial 3D mapping systems are widely available on the different platforms (airplane, helicopter, UAV, mobile-vehicle, etc.), which are mainly used to collect 3D imagery for civil mapping applications, including stereo-pair, point cloud, oblique, panoramas, motion video, and others.  With 3D imaging technology, those ‘combined’ systems mostly produce very accurate 3D imagery (point cloud), while reaching very high-resolution geospatial details on the ground. One of the main reasons for high accuracy with the spatial details is: Those mapping systems are commonly assembled with the Global Positioning System (GPS) and Inertial Navigation Systems (INS), in addition to high precision ‘civil-mapping’ sensors, scanners, or cameras. GPS The Global Positioning System can be used for determining one's precise location and providing a highly accurate time reference almost anywhere on Earth or in Earth orbit. The accuracy of the GPS signal itself is about 5 meters. However, using differential GPS and other error-correcting techniques, the accuracy can be improved to about 1 cm over short distances. INS An Inertial Navigation System provides the position, velocities and attitude of an aircraft by measuring the accelerations and rotations applied to the system's inertial frame. INS's have angular and linear accelerometers (for changes in position). Angular accelerometers measure how the aircraft is rotating in space. Generally, there's at least one sensor for each of the three axes: pitch (nose up and down), yaw (nose left and right) and roll (clockwise or counterclockwise from the cockpit). Linear accelerometers measure how the aircraft is moving in space. Since it can move in three axes (up & down, left & right, forward & back), there is a linear accelerometer for each axis. A computer continually calculates the aircraft's current position. First, for each of six axes, it integrates the sensed amount of acceleration over time to figure the current velocity. Then it integrates the velocity to figure the current position. After acquisition (before serving, analysis, or extracting information),  3D imagery from those mapping systems must be processed by remote sensing specialists with proper ‘algorithm-enabled’ computer package for higher accuracy, in addition to other aspects (noise removal, color enhancement  ....) Manage 3D Imaging and Point Clouds Different data of 3D Imaging (and Point Clouds) will utilize different serving approach, when trying to manage at server-side, which will ensure that each can be effectively and seamlessly used in various applications. In the market, some solution vendors offer specific server-side solution to manage certain type of 3D Imaging data directly at server-side, such as optical stereo-pair, optical oblique, optical panoramas, optical motion video, point cloud, or others. Pictometry at EagleView Technologies - Roof Measurement & Aerial Measurement Service GEOSPAN at GEOSPAN is the industry leading Photogrammetric provider of multi-angle oblique aerial and integrated 360° street-level   … CycloMedia at Home (EN) | CycloMedia - EN earthmine at earthmine - 3D Street Level Imagery Solutions Leica Cyclone (Cyclone-server) AXIS 241 Video Servers ... ... View more

3D Printing Topo map with/ without City Model is highly demanded, in practice, including the creation of sand table. However, most of 3D mapping systems like ESRI CityEngine, ArcScene or ArcGIS Pro does not support 'direct' 3D Printing for topo 3D map (with or without 3D features). A workaround solution to this task is addressed (refer to the article below from Roy). C Tech’s MVS software includes the ability to create specially formatted VRML files which allow for the creation of full-color 3D physical models using the most advanced 3D printers. However, C Tech only offers 3D model printing as a service to clients.  They assist with modification of the models to ensure the models print correctly the first time and perform the actual printing. What is 3D printing? How does 3D printing work? 3D printer creates 10 houses in a DAY | Daily Mail Online       ... View more

What are the major challenges to 3D GIS developments and applications, especially, in complicate facilities and surface-subsurface 3D systems? 3D spatial data modeling and realization (raster, topo,TIN, geometry) in one 3D solution system, and then smoothless interoperation in others! Among those, 3D design models (as 3D CAD models) and some 3D geo-models (as 3D G&G models) also must be considered (even, intergrated), even though those 'geometry' may be too details for some 3D GIS systems... The techniques and theories of 2D spatial data modelling are not able to fully be transferred onto the aspect of 3D data modelling and structuring. Besides, realizations of "true" 3D GIS spatial system needs a lot of efforts from 3D computer graphics, 3D computational geometry, 3D CAD, close-range photogrammetry, and Lidar, which are extensively taking place in energy and mining industries. A basic reference is available below ... View more