Articles in the Mapping Category

Mar 2008 | No Comment

Filipo Rodriguez, Gian Paolo Plaia

Application of cognitive psychology for reduction of mapping errors

Human factors contributing to mapping errors made by operators working on digital mapping systems were studied from Cognitive Psychology perspective to evolve suitable strategies to reduce errors.
Mapping errors
Study area
Large scale topographic maps of better than 1:5000 scale with 1 to 2 m contours are …

Nov 2007 | Comments Off on Determination of lag-time in kinematic GPS recording

Since the staring of GPS, many researchers have investigated its application in aerial photogrammetry. Today, with the full constellation of 24 GPS satellites operational, enabling excellent satellite geometry any time of the day, the need to apply the full potential of GPS for real time aircraft navigation and photogrammetric mapping can be realized. The use of GPS to determine relative positional data for ground control points in a photogrammetric block adjustment is widely accepted and practiced. The camera exposure station coordinates derived by Airborne Kinematic GPS drastically reduces, the number of horizontal and vertical control points needed in aerial triangulation.

In large-scale mapping, the accuracy level of control data required is very high. The lag in time between the camera exposure and the GPS epoch recording in the GPS receiver is critical in deriving accurate coordinates for the exposure station (principal point) coordinates. Due to delay in the electronic transfer of data from camera clicking to GPS receiver in recording the event makes the Lag in time to occur. To meet the high accuracy requirements for the largescale photography and mapping projects the lag in GPS recording time should be derived and applied. In this study, an attempt is made to compute the Lag-time in airborne kinematic GPS derived exposure stations from aerial triangulation.

Aerial triangulation is carried in Digital Photogrammetry work station with conventional method of using ground control points, and the exposure station coordinates are derived. Lag-time is computed by finding difference in coordinates of exposure stations derived from conventional aerial triangulation and from airborne kinematic GPS. The results of this project will help to improve the locational accuracy of GPS derived exposure stations in aerial triangulation.

Aerial photography is carried out in the study area on 1:6000 scale with forward overlap at 60% and lateral overlap at 20% using RMK TOP30/23 camera. During aerial photography the airborne GPS is operated to record the exposure coordinates.

The computer controlled navigation system (CCNS) is loaded with flight planning data from World Wide Mission Planning (WWMP). During aerial photography CCNS takes coordinates of aircraft position from navigation system and navigate pilot for alignment as per flight plan. Based on navigation coordinates, CCNS sends signals to camera for exposure. The camera exposure system is connected to Trimble 4000 SSI dual frequency GPS system on board, which records GPS data continuously at 1.0sec sampling rate. During the camera exposure, camera system sends signal to the onboard GPS system, which record each exposure as an event marker in the GPS

Jul 2007 | Comments Off on Topographical mapping

SOME of the earliest known maps were made in Iraq which was drawn during 2400 BC for the purpose of land taxation. A Roman map dating 350 AD showed such topographical features as roads, cities, rivers and mountains. Although the basics of land surveying were known but the large scale maps before 16th century were limited to cities and other small areas. Up to the middle of 16th Century, there was little real knowledge of the geography of the most part of the world.

May 2007 | Comments Off on VISAT: Mapping what you see

With the continued growth of urban centers all around the world, city planners are required to keep up with up-to-date geographical at a faster rate. This has led to the establishment of spatially-referenced Geographic Information Systems (GIS) for a variety of municipal applications. This information, however, is expensive to obtain by conventional methods. In addition, conventional methods supply only point solutions and are therefore not suited to support the increasingly complex requirements posed by urban centers in a timely fashion. Satellite remote sensing and aerial photogrammetry are two methods which can provide various GIS information at high rates and reasonable cost. However, with the first method, the associated accuracy is not suitable for many applications, and in the second case the near vertical field of view provides only part of the information required.

Mar 2007 | Comments Off on Beyond mapping

Over the years topographic mapping generally involved acquisition of data related to the features of the earth, its environs of user’s interest and its graphic depiction on a suitable media, generally paper, ensuring that the accuracy specifications, which depend upon the type of end product, are strictly adhered to.
Over the years topographic mapping generally involved acquisition of data related to the features of the earth, its environs of user’s interest and its graphic depiction on a suitable media, generally paper, ensuring that the accuracy specifications, which depend upon the type of end product, are strictly adhered to.

Nov 2006 | Comments Off on The 3rd dimension

Spatial data is the fuel for 3D Applications, but all too often the fuel supplied is inappropriate. The software applied and expertise required when modelling a flood event or predicting a cityscape’s lineof-site is exactly the same using highly precise data as it is for generalised data. The difference is in how well that analysis relates to the real world … i.e. whether the analysis is correct or not. Conversely, supplying highly accurate or dense data to a generalised analysis can cost both time and money which is not reflected in the final product. Hence the word of this paper is: appropriate. Apply the most appropriate data to your application. There is nothing wrong with “approximate” or “inexpensive” 3D data, as long as it is appropriate for the level of analysis being performed.

Sep 2006 | Comments Off on Cartography as a tool in study of dredging

Mumbai acquired its port importance only with the advent of the Portuguese in 1508. Francis Almeida sailed into this harbour and called it as Bom Bahia or the Good Bay. The British corrupted the Portuguese name “Bom Baia” to “Bombay”. The Kolis used to call the islands “Mumba” after Mumbadevi.
It was the British who developed it into a centre of commerce to rival any other centres in the country then. The British embarked upon large-scale reclamations and engineering works to consolidate the seven islands. In 1803 Bombay was connected with Salsette by a causeway at Sion. A causeway now called Colaba Causeway joined the island of Colaba to Bombay in 1838 and the Causeway connecting Mahim and Bandra was completed in 1845. This gave access to the rich hinterland of the Deccan providing further impetus for the growth of then Bombay.

Jun 2006 | Comments Off on Going hand in hand

With the launch of GPS in the 1980s, the task of providing control points for mapping purposes was greatly simplified, leading to economy and ease of operation. The technique of LASER mapping, which existed decades before GPS, also received a boost due to GPS, as instantaneous precise positioning of the exposure station during the mobile LASER mapping operation was made possible by GPS, thus solving a major problem in LASER mapping…

Apr 2006 | Comments Off on Advent of modern cartography in nautical charting

A nautical chart is a medium of information and tool for safe maritime navigation. It is the chief nautical instrument for ocean route planning and safe navigation. With the time not only the user’s requirements have increased, but also the advancement in the expertise in the field of nautical cartography has resulted in better product in the most useful way. With the advent of modern cartography, chart contents are stored in…

Dec 2005 | Comments Off on Photogrammetric Mapping

A case study of El Salvador City has been done using various photogrammetric techniques. This project comprised the complete new mapping of the town including all features like buildings, boulevards, roads,manhole/ drainage, light / telephone polls, trees /tree areas, ponds, river and streams (with break lines), Monuments, playground / Parks etc. The vectorization of the model has been done on Digital (Socket Set) and analytical systems both. From speed point of views digital systems are as good as analytical systems. It also depends on the skills / expertise of the Operator who is preparing the maps.