2002 DFDC Workshop, Nottingham – abstracts

Capturing digital data in the field - digital field data capture for Geological Surveying in North-western Guinea 1998–2001

Dr Klaus-Dieter Meinhold, BGR, Hannover, Germany

A geological surveying project was carried out in Guinea between 1998 and 2001 in co-operation of the Federal Institute for Geosciences and Natural Resources (BGR), Hannover, Germany, and the Direction Nationale de la Recherche Géologique et des Hydrocarbures, Conakry, Guinea.

Aims of the project:

  • Training of up to ten Guinean geologists and geotechnicians in geological surveying, evaluation of field and laboratory data, and the use of computers to process the data.
  • Geological surveying and production of two geological maps with Explanatory Notes as a model for a national system of geological maps at a scale of 1:100 000.
  • Setting up of a GIS and a database structure for geological surveying in Guinea to be integrated into the national geological database.
  • Inventory of mineral resources in the project area.

Project staff: BGR staff in Guinea

Long term:
Dr Joern Brinckmann; Dr Klaus-Dieter Meinhold (geologists)

Short term:
Ms Stefanie Bellenberg, Ms Dagmar Bolsmann, (cartographers)
Dr Hans-Peter Burgath (petrographer)
Dr Wolfgang Hirdes; Dr Lothar Lahner (geologists)
Dr Markus Toloczyki (geologist; GIS expert)

Project staff: Guinean counterparts

Madani Baldé, Tso Tso Bangoura, Karamoko Conde, Mahmoud Diawara, Alpha Makanéra, Omar N'doungou Camara, Mahmoud Touré (Ingénieurs géologues)

Nassirou Bah, Bakary Ibrahim Sylla (Géologues techniciens)

Project area:

The project area lies in north-western Guinea between Koundara in the north-west and Touba in the south-east (13°15'W - 12°45'W, 11°30'N - 12°30'N). It is covered by two map sheets at a scale of 1 : 100 000. The rocks in the area are of Precambrian to Quaternary age.

Morphologically, the project area has three different types of landscape: a plain in the north-west (elevation 60 to 100 m asl), two steep, parallel mountain ridges (Basserride and Koubia) in the centre (up to 750 m asl), and a moderately undulating highland (>700 m asl) in the east and south-east.

The plains, the ridges and the highlands are covered by savannah vegetation and bush, the wide valleys between the ridges and between the ridges and the highland by thick rainforest, secondary bamboo forest, and elephant grass.

There is a rainy season from June to November and a dry season from December to May. Temperatures reach over 40°C in the dry season, at the end of which (mid-April to June) humidity becomes rather high.

Fieldwork

Fieldwork was carried out from December to June. Access in the area was rather poor, the area is crossed by two gravel roads and a few seasonally passable tracks. Most of the surveying had to be done on foot and, partly, along the larger rivers, by dugout canoe. We worked from two tent camps hosting three working groups each under the expert guidance of a German geologist. Field equipment comprised the usual camp equipment and four cross-country vehicles. Power was supplied by generators or car batteries. Each camp had one laptop computer.

Project office

The project office was in Labé, a small town in the highlands about 100 km east of the project area. During the rainy season and the first two months of the dry season, energy was supplied by a power station, but when the dam site at Pita was dry from March to June, we had to use generators and solar panels. Internet and e-mail facilities were not available, telephone was frequently out of service.

Digital equipment: hardware

In the office:

  • 1 HP PC, used as server for a small network
  • voltage stabilizer
  • inkjet plotter, DIN A0
  • laser printer, DIN A4
  • scanner, DIN A4

In the field:

  • 2 robust laptop computers
  • 6 GPS receivers, Garmin II

Digital equipment: software

  • WINDOWS NT 4.0 workstation, French
  • MS Office Professional, French
  • ESRI ARCView 3.0a GIS with German and French language supplements
  • ESRI Data Automation Kit, English
  • ESRI Spatial Analyst, English
  • PROMPT, French
  • BGRproject.exe: a user platform for linking the MS ACCESS database with ARCView (programmed by MAPS Geosystems, Munich and Beirut)
  • several extensions to ARCView for connection with orthophotographs and Digital Terrane Model as well as for import of GPS Data (programmed by MAPS Geosystems)
  • the ARCView extension 'STREICHZEICHEN' for displaying and printing symbols of tectonic elements (dip direction and dip of schistosity, fault and bedding planes, dykes, and fold axes) in ARCView maps directly from the database (programmed by a Hannover company)
  • 'FUGAWI' to link the GPS with the laptops and to download waypoint and track files from GPS to computer
  • 'Rockware 2.0': for statistical evaluation of tectonic data
  • 'MINPET 2': to evaluate petrographic and geochemical data

The database was structured in co-operation between BGR and MAPS Geosystems.

Training in digital methods

The BGR experts were trained in Munich by MAPS Geosystems in the use of ARCView, the database and data capture using BGRproject.exe. The counterpart personnel were trained in these systems and in the use of GPS in a three-week course conducted by a Lebanese expert from MAPS Geosystems in Labé. Training was continued on-the-job in the field.

Topographical base

One major problem arose because there was no adequate topographical base for the project area. Therefore, BGR ordered a Digital Terrane Model (DTM) of the area from the German-Lebanese company MAPS Geosystems, to be produced using georeferenced orthophotographs made by a Japanese company. Besides the DTM (with hillshade), MAPS Geosystems supplied a topographic base with contour lines (20, 50, and 100 m asl), UTM grid lines (1, 5, and 10 km), and a geographical grid. In BGR, the line data for drainage system was calculated from the DTM using the ARCInfo modules GRID and TIN. But this was not sufficient, especially in the areas with negligible relief.

Field data capture: improvement of topographic base

Line data for roads and tracks were recorded in the field using GPS by following the routes by car with the GPS equipment continuously operating, powered by car battery via the cigarette lighter. In camp, these trackfiles were downloaded to the laptop and converted to ASCII files using the program FUGAWI. They were then imported into ARCView as shapefiles. These were the only line data directly captured in the field.

The co-ordinates of topo-points (villages, water wells, bridges, fords, waterfalls, road crossings, antennae, mosques) were determined and stored by GPS on site. Descriptive notes (numbers, annotation, etc.) were recorded on schedule forms and in field books. In the camp, the waypoints were downloaded to the laptop (using the program FUGAWI) and the topo-point data recorded were entered by hand into the database. Waypoints (ASCII files) were directly imported into ARCView (using the extension from MAPS Geosystems), topo-points from database via an SQL connection, both as shapefiles.

In the office, the line data calculated from the DTM for the drainage system was corrected in the following way:

  • Stereographic interpretation of the correct drainage system from aerial photographs by using reference points from digitized orthophotographs to determine the correct scale of the aerial photographs.
  • Digitisation of the corrected drainage system using ARCInfo and conversion to shapefile format for use in ARCView.

Field data capture: geological field data capture

The co-ordinates of the outcrops were determined by GPS and stored as waypoints. The name and number of the site, sample numbers, measurements of tectonic elements, geological, morphological and sample descriptions were recorded in field schedule forms, field notebooks, topographic maps and/or aerial photographs.

In camp, all of the geographic and attribute data were entered every evening into the database, and via an SQL connection imported into ARCView as shapefiles. Waypoints from the GPS were also imported (s. 8.1) as shapesfiles and as an overlay for control of the point co-ordinates. After three weeks in the field, the captured data were synchronised with the main database on the server in the office and with the other laptop of the other camp. Maps were then plotted from ARCView. After a week of work in the office, the geologists returned to the field with a new map showing the newest information, and an updated database on their laptops containing the newest data of all six working groups.

Line data (e.g., geological boundaries, faults, dykes) and polygon data (geologic units) were not captured digitally in the field, but recorded on topographic maps, and later digitized in the office by scanning and vectorising or by using a digitiser table.

Results

In total, field data from more than 6000 sites were captured and stored together with the results of petrographic and geochemical analyses in the database. After evaluation of all the data, the final geological manuscript maps were drawn by the geologists, digitised and reworked for printing by BGR cartographers using ARCInfo. Explanatory Notes are in progress. All data are available on CD-ROM. They will be incorporated into the national geological GIS database in Conakry.

Planning for a digital system to be used for geological surveying projects within the framework of development aid

It is planned to develop a digital system for geological surveying and GIS projects conducted by BGR within the framework of development aid using the experience gained in projects in Argentina, Chile, Guinea, Ivory Coast and Yemen.

The following activities are in progress:

  • improving the interface of GPS with ARCView
  • reprogramming ARCView extension for tectonic elements (using AVENUE)
  • improving geo-referencing of scanned maps using a new program (including a GPS connection)
  • restructuring of the database according to experience gained in projects in Guinea, Argentina, Chile, Ivory Coast and Yemen
  • development of a new module for co-ordinate conversion, including geographical, Gauss-Krueger, and UTM co-ordinates for different map projections (by a software development company)
  • use of digital cameras has been started in several projects. A database module has been programmed (in Visual Basic for Applications) to read photographs and scanned images into ACCESS. Photographs and scanned images (drawings, sketch maps, etc.) are stored externally to the system.

The following activities are in the planning stage:

  • linking to the program ROCKWARE (newest version) for statistical evaluation of tectonic elements
  • linking of modules for statistical evaluation of geochemical data
  • linking of GEODIN (a program for preparing borehole descriptions) with ARCView to for automatically draw borehole profiles and interactively design cross sections
  • preparation of German, English, French and Spanish versions of the program system
  • testing of the use of minicomputers for direct data capture on site.