Turning GeoTIFF into TIFF + worldfile (QGIS)

hi all,

after some weeks I go on with the videotutorial from the Project Tovel. Until now we saw how to download some Open Data for our GIS, how to load georeferenced raster level in QGIS, how to georeference historical maps.

Today I will show something particular, that probably many of you will not need very often working on landscape archaeological project, but that will be more important to manage excavation GIS: how to turn a GeoTIFF picture into a TIFF + worldfile image.

As some of you will know a GeoTIFF is a particular kind of raster data in which the georeferencing values are embedded within the TIFF itself. This option can be a nice solution for a topographer but it is extremely annoying for archaeologists. The reason is simple: topographers often work on pictures or maps that are ready to be used, without the necessity of any photo-editing, which (on the contrary) is an important phase in archaeological photo-mapping process (e.g. for the "Aramus method"). The primary difference between a GeoTIFF and a TIFF + worldfile image is that it is not possible to modify the first one without loosing the georeferencing values (which are integrated in the picture), while it is possible to perform some photo-editing operations (change the colors, balance the brightness and contrast, etc...) in the second one, without problems, being the geolocalization data stored in a separate file (the worldfile).
For this reason working with raster images and worldfile is often the best choice for archaeological GIS (especially for excavation), where it can be useful to "erase" all the part of the photo which are outside the area of interest (e.g. outside the rectification region) and to take advantage of transparency in overlapping different raster levels (which can correspond to different stratigraphic levels).
As I wrote previously, the videotutorial I prepared using the data of Project Tovel simply shows how to turn a GeoTIFF, currently the unique option for QGIS georeferencing module) into a TIFF and a worldfile, a more useful format, without exiting the software.

Have a nice day!

OpenJUMP: query to extract single points from a general vector layer

Hi all,

today I am working on data elaboration of an archaeological excavation. I decided to record a short videotutorial to show how to perform a very simple query in OpenJUMP (which is a topic I am often asked to explain during lessons about archeology and open source). Before to start, I'll write a short introduction regarding the processing of this data, just to understand why I need to perform this kind of query. 

I worked on this excavations collecting all the data in a local system (with simple 3D Cartesian coordinates), because the job was an emergency archeology project and I did not have the time to set up a geographic coordinate system on the field, before the construction site began. Just at the and of the excavation, I could come with a RTK GPS, to collect some Ground Control Points (GCP) in UTM WGS84. This is the reason why in this time, when I am processing the data, I had to put together all the daily total station downloads in a single cvs file, which I georeferenced in OpenJUMP, using the GCP I collected with the GPS. The problem is that now I will have to separate again the single points, grouping them according to their function (e.g. points for photomapping of area 1, height points of the same area, points for SfM georeferencing, find-points and so on...). To do this operation, I will simply use OpenJUMp (where I loaded and georeferenced the csv file), performing a query on the attribute (the name) of cumulative vector layer , which will tell me where are the the points I need. In this way I can select in the GIS the features I am looking for and put them in a new vector level, copying the db schema of the cumulative layer (name, y, x, z, code). At the end of the process, I will have single separated vector files which I will use in the next steps of data processing (photomapping, 3D, ecc...).

Here is the videotutorial I uploaded in the ArcheOS tutorila wiki (rom Insbruck University):

I hope it was useful, have a nice day!

Photomapping with Quantum GIS (Khovle method)

Hi everybody
Together with Alexamder Sachsenmaier and Alesandro Bezzi i found out a method to create a photomosaic just with QGIS. The problem was to export the single pictures in a good quality and in the size of the whole photomosaic not just the size of the single picture. But this works fine with the print composer of QGIS
So shortly:
1. edith the file of the ground control points to a .csv file
2. import the .csv file into QGIS (plugin is requiered)
3. change the design of the points
4. start the print composer and export the model with the points. Here its possible to set the dpi: e.g. for an area of 3x2m 500dpi gives a resolution of more or less 1mm
5. start the georeferencing plugin of QGIS and georeference the model
6. to export the wordfile from the geotiff of the model, type the following in the terminal
gdal_translate -co "TFW=YES" input_geotif.tif output_tif_tfw.tif
or open the model in OpenJUMP and close it again
7. georeference all the single pictures with QGIS
8. start the same print composer like the one for the model and export all single picures (dont move the pictures)
9. open the model in GIMP and import all single pictures as single layers
10. give the same name to the wordfile of the model and the photomosaic
Alessandro allready maked a videotutorial:

So, I hope this is helpful for somebody...

New tutorial in the Mesh Editing session of DADP

Hi all,
after my teaching in the Master Open Téchne 2013 about Computer Vision (SfM and IBM), i'm updating the Mesh Editing session (english page) inside the Digital Archaeological Documentation Project.

Up to now I inserted four videotutorials:

how to create a poisson mesh inside MeshLab

how to georeference a point cloud in CloudCompare using a Cartesian coordinates system

how to erase not useful points inside CloudCompare

MeshLab: difference between vertex color, raster color and texture 

how to import Bundler's camera positions inside MeshLab

i hope this is useful :)