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Movements, leaders, victories and the continuing fight for equality.
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Meet the people whose lives, choices and achievements shaped the journey.
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In August 1908, a white mob attacked Springfield, Illinois’s Black community, destroying homes and businesses and lynching two Black men. National outrage over the violence helped spur the movement that created the NAACP the following year.
MORE →Reflects the personal views, recollections, and perspective of the author, Mike Davis.
This is a personal recollection on the Move fire on May 13, 1985
 | This article needs more citations. (September 2012) |
| VisionMap A3 Digital Mapping System | |
|---|---|
| Type | Airborne Digital Camera and Ground Processing System |
Area served | Worldwide |
| Website | www.visionmap.com |
A3 Digital Mapping System consists of a digital airborne camera and an automatic ground processing system[1] produced by VisionMap. The A3 camera captures imagery using a sweep mechanism, which collects high resolution vertical and oblique imagery simultaneously. The captured data is post-processed by the A3 LightSpeed ground processing system in order to create the final output products. The A3 System is used by numerous national and regional mapping agencies, as well as commercial mapping firms.
The A3 camera consists of dual CCDs with two 300mm lenses mounted on a special motor controlled axis that is attached to the frame, a fast compression and storage unit, and a dual frequency GPS. During flight, sequences of frames are exposed in a cross-track direction at a very high speed, providing a FOV of up to 106 degrees. High resolution vertical and oblique images are captured simultaneously. The camera’s wide field of view maximizes the distance between consecutive flight lines. The camera weighs 38 kilograms, and measures 50x60x60 cm.
Among the A3 System’s various final products are Super Large Frames (SLF), which are composed of all double frames of one sweep. The size of the SLF is 7,812 pixels along the flight and 62,517 pixels across the flight direction. The typical overlap between two consecutive SLFs in one strip is 30-60%. The overlap between two SLFs in adjacent flight lines is 30-60%. The SLFs may be used for stereo interpretation and stereo photogrammetry map production.[2]
A3 Digital Mapping Camera utilizes a unique mirror based optical compensation and stabilization method for all movements potentially affecting image quality (forward motion, sweep motion, and general vibrations of the aircraft). The method uses acceleration sensors, GPS data (for aircraft velocity calculation), and the motor encoders for calculation and control of the required motion compensation. Both linear and angular compensations are done by tilting the mirror mounted on the folding optics.
A3 LightSpeed processing system consists of a PC server configuration and software, which automatically processes data obtained during flight into photogrammetric mapping products. After a pre-process stage in which the user specifies the required outputs and output specifications, the system solves the AT and bundle adjustment automatically. Then a manual geo-referencing stage may be carried out, followed by an automatic processing of DSM, DTM and orthophoto.[3]
A3 LightSpeed processing system produces the following output products:
1. Accurately solved vertical and oblique single images of the area of interest. The solution for each image is the result of the photogrammetric bundle block adjustment with self-calibration.
2. SLFs (Super Large Frames), used for stereo photogrammetric mapping.
3. DSM (Digital Surface Model)
4. DTM (Digital Terrain Model)
5. Orthophoto with resolution up to the source frame resolution. Global and local radiometric corrections are applied to all frames. The mosaicing process is fully automated and is based on the topographic data (DTM) and radiometric analysis of the area.
In order to achieve high accuracy, all images and coordinates of projection centers, obtained by GPS, take part in the simultaneous bundle block adjustment with self-calibration. No INS is required.
As a huge number of single frames are obtained, with significant overlaps between them, a huge amount of common bundles are yielded. This leads to very high redundancy and robustness of the solved system and, therefore, to high final accuracy.
The A3 System was tested by the University of Stuttgart Institute for Photogrammetry (IFP) in their test field. The results of their test are as follows:
| Camera | Altitude(m) | GSD(cm) | RMS East(m) | RMS North(m) | RMS Z(m) |
|---|---|---|---|---|---|
| A3 | 1,972 | 6 | 0.017 | 0.023 | 0.050 |
| DMC | 870 | 8 | 0.028 | 0.044 | 0.054 |
| Ultracam-X | 1,200 | 8 | 0.060 | 0.025 | 0.044 |
| ADS40 | 770 | 8 | 0.027 | 0.031 | 0.050 |
Source: Wikipedia. Article content is retrieved live through the MediaWiki API.
A3 Digital Mapping System consists of a digital airborne camera and an automatic ground processing system produced by VisionMap. The A3 camera captures imagery using a sweep mechanism, which collects high resolution vertical and oblique imagery simultaneously. The captured data is post-processed by the A3 LightSpeed ground processing system in order to create the final output products. The A3 System is used by numerous national and regional mapping agencies, as well as commercial mapping firms.
Digital soil mapping (DSM) in soil science, also referred to as predictive soil mapping or pedometric mapping, is the computer-assisted production of digital maps of soil types and soil properties. Soil mapping, in general, involves the creation and population of spatial soil information by the use of field and laboratory observational methods coupled with spatial and non-spatial soil inference systems. The international Working Group on Digital Soil Mapping (WG-DSM) defines digital soil mapping as "the creation and the population of a geographically referenced soil databases generated at a given resolution by using field and laboratory observation methods coupled with environmental data through quantitative relationships."
Mapping Bangladesh (Bengali: ম্যাপিং বাংলাদেশ) is an online-based community in Bangladesh constituted of mappers working to develop a digital mapping system through contributions of citizen cartographers on Google Map Maker.
Japan is an island country of 14,125 islands, of which approximately 260 are inhabited. Japan is the third-largest island country in the world, behind Indonesia and Madagascar. Japan is also the second-most-populous island country in the world, behind only Indonesia. According to a survey conducted by the Japan Coast Guard in 1987, the number of islands in Japan was 6,852. At that time, the survey only counted islands with coastlines of 100 meters or more that were shown on paper maps. On February 28, 2023, the Geospatial Information Authority of Japan announced that the number of islands had been updated to 14,125 through a recount using digital maps. Since there is no international standard for counting islands, only islands with a coastline of 100 meters or more were counted, as in the past. According to the GSI, advances in surveying technology and the detailed representation of topographic features through digital mapping contributed to this announcement.
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →The Greenwood District.
