Dear colleagues,
In the Colombian Geological Survey (CGS) we are establishing a standardized methodology for geologic mapping at different scales (1:100 000, 1:50 000, and 1:25 000) because every work group has its own methodology and the CGS wants to agree on a unique basic methodology that everybody can follow to.
We have been assigned the task of reviewing the density of field data collection at different scales.
The big question about geological mapping procedures is the field density data collection at different scales.
Do you know about the documents or information that discuss specifically geological mapping?
We really appreciated your help.
Kind regards,
Jorge GÓMEZ TAPIAS
Tomás CORREA
Diana MONTOYA ARENAS
César TARAZONA
Colombian Geological Survey
Dear friends,
it depends on the geology and what statement you want to make.
A stratigraphic mapping of horizontally deposited strata certainly needs less control points than a mapping of folded and disturbed deposits or of mining complexes
Wolfgang
Hola Jorge, creo que eso depende mucho de la zona de mapeo, los objetivos y calidad de afloramientos. No hay una regla escrita sobre eso. Al final, lo importante es que el dato sea representativo, y permita hacer las interpretaciones pertinentes.
Saludos
Jorge Gómez Tapias wrote: "...The big question about geological mapping procedures is the field density data collection at different scales..."
I recommend the Minimum Curvature gridding option. The default grid cell size that you must define will be according to the size of your zone of interest (km by km) and the number of points that your geological feature has.
The grid cell size (GCS) (the distance between grid points in the X and Y directions) should normally be ¼ to ½ of the line separation or the nominal data sample interval. If not specified by your software, the data points are assumed to be evenly distributed and the default cell size will be set to:
GCS = ¼ by the square root of the division grid area/number of values.
To illustrate in an example: if your zone of interest has 100 km by 100 km and you have 1,000 points of samples, your GSC will be 3162 m; but if you have 2,000 samples, your GCS will be 2236 m; and if you have 4,000-point samples your GCS will be 1581 m.
There are other factors such as blanking distance, and tolerance required for each grid cell (absolute error in grid data units; the number of iterations, but according to your outputs you will be more comfortable or not.
Please, let me know if you have doubts about my answer.
Best regards, Mario E. Sigismondi
PS: I write you in English but I understand Spanish my native language in Argentina.
Dear Jorge, please, check this RG answer perhaps it is a good explanation for your question:
https://www.researchgate.net/post/Role_of_data_point_distribution_in_Geo-potential_anomaly_pattern_gravity_and_magnetic_anomaly_map
Best wishes, Mario
I recommend checking this paper:
@article{Hengl2006, author = {Tomislav Hengl}, doi = {10.1016/j.cageo.2005.11.008}, issn = {00983004}, issue = {9}, journal = {Computers and Geosciences}, keywords = {Grid resolution,Inspection density,Point pattern analysis,Scale,Terrain complexity,Variogram}, month = {11}, pages = {1283-1298}, title = {Finding the right pixel size}, volume = {32}, year = {2006}, }
Dear Jorge,
I think you are looking for defined grid patterns for mapping.
But I would like to tell you about a special mapping.
I had to mappe an area of 1500 square kilometers at a scale of 1:5000 according to sedimentary petrographic criteria for a drinking-water risk analysis project.
Geologically, it was the Upper Freshwatermolasse of Bavaria, a neogene system of rapidly changing deposits of braided river- with meandering river-systems and partial overburden of quaternary loess and alluvial-filled depressions.
I had to map the sediments as they come.
In some areas even a narrow grid of e.g. 50 m could have distorted the result, in others a 100 m grid would be sufficent.
I should mention that the area is used for wells for municipal drinking water supply and therefore the data should be as accurate as possible for further processing.
Many greetings,
Wolfgang
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