Semi Automatic Digitizing of Contours from 1:25000 Scaled Maps

In aerial photogrammetry, the trend is moving away from analog to digital systems especially in the production of topographic map. Many private or government mapping organizations around the world have started using digital mapping camera system even though the price is very expensive. These organization change their way of producing topographic map because the digital mapping camera offers various advantages such as cost saving, time saving, high quality photogrammetric output such as maps, contour lines, digital terrain model (DTM), orthophoto etc, new application areas and it could eliminate analog step in the image processing production line. Due to these advantages, in 2007 the Department of Surveying and Mapping Malaysia (DSMM) has purchased the digital mapping camera system of Zeiss Integraph. DSMM purchased the digital mapping system with the objectives to speed up the process of mapping the country and to provide the best quality photogrammetric output using state of the art technology in aerial photogrammetry. This paper discusses about the experience of producing large scale map using mono and stereo digitizing based on aerial photograph captured by the digital mapping camera. In general, it is a common practice in aerial photogrammetry to use stereo digitizing technique in producing photogrammetric output. The Department of Surveying and Mapping Malaysia (DSMM) uses this technique to generate three dimensional (3D) stereomodel and subsequently digitizing is performed for natural features such as rivers, lakes, vegetation etc and man-made features such as roads, buildings, bridges, drainage etc. Also from the 3D stereomodel contour lines, DTM and orthophoto are generated. The data captured from the 3D stereomodel are normally used for topographic map production, updating spatial databases and various applications. In stereo digitizing method, the 3D stereomodel could be viewed in three dimensional, hence, 3D (XYZ) coordinates could be captured and stored for further processes. Today, orthophoto becomes increasingly importance for various applications. It is a common practice that orthophoto is used as an input for GIS. Also the orthophoto could be used for large scale utility mapping and normally it is used as base map layer within GIS application. In this study, 3D stereomodel is used to generate contour line, DTM and orthophoto. All the features in the 3D stereomodel were also digitized. Then mono digitizing is carried out to digitize topographic features (i.e natural and man-made features) from the orthophoto. In mono digitizing, utilities such as pipe line, electrical cable, sewerage etc were digitized too. The mono digitizing method provides planimetric coordinate in two dimensional (2D). For the height or Z value, it is obtained from the DTM. The digitized man-made and natural features from both mono and stereo digitizing were compared for accuracy assessment. It is expected that the results of stereo digitizing is superior compared to mono digitizing. The achievable accuracy depends on many factors in every level of data processing such as acquisition of aerial photography, control point selection, aerial triangulation adjustment and digitizing. The final result of this study is a large scale utility map. In conclusion, the digital mapping camera could provide quality results for large scale mapping, map compilation and map revision.

2012 16th International Conference on Information Visualisation, 2012

In this paper we describe a simple modeling technique used to create precise and complex digital terrains models using contour maps. As a case study we use the terrain of the "Monte Albán" archeological site, located in the Mexican state of Oaxaca. We employ the technique with a simple contour map to obtain a realistic tridimensional terrain model that includes the four main hills of the site.

3D simulations requested in various applications had led to the development of fast and accurate terrain topography measurement techniques. In this paper, we are presenting a novel framework dedicated to the semiautomatic processing of scanned maps, extracting the contour lines vectors and building a digital elevation model on their basis, fulfilled by a number of stages discussed in detail throughout the work. Despite the good results obtained on a large amount of scanned maps, a completely automatic map processing technique is unrealistic and remains an open problem.

2006

1.0 Introduction Isolines have proved to be a highly effective way of conveying the shape of a surface (most commonly in the form of height contours to convey geographical landscape). Selecting the right contour interval is a compromise between showing sufficient detail in flat regions, whilst avoiding excessive crowding of lines in steep and morphologically complex areas. The traditional way of avoiding coalescence and confusion across steep regions has been to manually remove short sections of intermediate contours, while retaining index contours. But incorporating humans in automated environments is not viable. One approach has been to automate manual approaches using map generalisation methodologies. This research reports on the design, implementation and evaluation of an automated solution to this problem involving the automatic identification of coalescing lines, and removal of line segments to ensure clarity in the interpretation of the geographical surface. The algorithm was...

The surface of the earth has landforms and features of many different types, that vary widely in elevations. Contour maps can show the elevations of these features, which allows looking at a 2D map to visualize the Earth in 3D. To draw the contour maps, it is necessary to calculate the horizontal coordinates to determine the location of the point and the altitude, which is the level, and these coordinates are measured in the field, where the time taken to measure them is a large time, so other methods are used that are easier and faster. Contour mapping with photogrammetry techniques when two images of a location are captured from different angles. the drone makes the acquisition of aerial images more efficient than ever. In addition to cost savings, also benefit by reducing risks to survey teams.Several photogrammetric software is available for drone ( UAV ) data processing, which provides different accuracy to create a 2D map such as Agisoft Photoscan version 1.2.5.2735, Pix4D version 4.4.12, and others. The paper will be focusing on the use of drones and close range photogrammetric techniques to effectively generate a contour map. Agisoft Photoscan was used for processing data and described briefly in this paper. The results obtained were compared with field survey measurements. In conclusion, an accurate contour map was produced within a short time using photogrammetry techniques, and the results of total root means square error (RMS) of check points was found as follows : total (RMSE) of the (X) coordinate is (0.55 m), the (Y) coordinate is (0.48 m), and the (Z) coordinate is (0.32 m(depending on the area of the site. It can be a combination of drones with photogrammetry software can be employed for various fields and geoinformation.

We present two new methods for approximating elevation data from contours to a grid. The first repeatedly interpolates new contour lines between the original ones. The second starts with any interpolated or approximated surface, determines its gradient lines, and does a Catmull-Rom spline interpolation along them to improve the elevations. We compare the new methods to a more classical thin-plate approximation on various data sets. The new methods appear visually smoother, with the undesirable terracing effect much reduced.

Presented at the 19th ICA Meeting …, 1999

It is believed that Web-based visualisation of spatial information could be greatly enhanced through the use of dynamic or 'onthe-fly' map generalisation. This involves dynamically deriving scale-and theme-dependent displays from a single detailed dataset, thus eliminating the need to maintain duplicate datasets at different resolutions. Dynamic generalisation also prevents the generation of cartographically-poor maps that result from the display of spatial information at a considerably different resolution from that at which it was captured. The implementation involves combining automated generalisation and symbolisation techniques together in a simple rule-base to produce a virtual map of central Edinburgh in which both the level of detail and the symbology is dynamically tailored to a user-specified scale and map theme (tourist or topographic maps). The paper explores the inherent differences between the generalisation of a virtual map and that of a paper map, and also considers issues such as those arising from the relationship between map scale, map theme and utility. The research demonstrates that it is possible to achieve effective results using a limited number of simple mechanisms, and argues that the true potential of dynamic generalisation lies in two main areas -firstly, in an ability to narrowly-define the map theme, thus enhancing map clarity and more closely matching user requirements; and secondly, in using control over the map scale as a gateway to other types of map use and other themes.

2009

An automated system has been developed to generate grid DTM data from a rasterized topographic map. Conventional methods used are based on either "raster-vector conversion " or "line following " and require a lot of manual input and computing time. The system developed here is based on automated recognition of color contour lines from a rasterized topographic map and automated tracing of the sectional heights of the recognized lines.

Scientific Investigations Report, 2012

The capability to easily create digital contours using commercial off-the-shelf (COTS) software has existed for decades. Out-of-the-box raw contours are suitable for many scientific applications without pre-or post-processing; however, cartographic applications typically require additional improvements. For example, raw contours generally require smoothing before placement on a map. Cartographic contours must also conform to certain spatial/logical rules; for example, contours may not cross waterbodies. The objective was to create contours that match as closely as possible the cartographic contours produced by manual methods on the 1:24,000-scale, 7.5-minute Topographic Map series. This report outlines the basic approach, describes a variety of problems that were encountered, and discusses solutions. Many of the challenges described herein were the result of imperfect input raster elevation data and the requirement to have the contours integrated with hydrographic features from the National Hydrography Dataset (NHD).

2015

This work is part of a research branch that studies how to acquire metric, semantic and symbolic information from historical maps without damaging the physical support. The technological growth regarding both mechanical instruments and digital high-resolution sensors allowed the development of suitable tools for the digitization of historical maps and creation of more accurate digital models; therefore, by now, the use of automatic systems for acquisition of digital data is continuously spreading. In the work described in this paper we used a robotic arm (UR10), on which we mounted a digital camera in order to acquire high-resolution images of any object following a regular grid. The arm movement was programmed to keep the rotation angles of the camera constant while shifting it at pre-defined quantities along the two axes. The tests performed demonstrated that we could obtain a three-dimensional model with an accuracy below the millimetre in an almost automatic way.