Lloyd Bosworth : archaeologist | human | beard

Posts in the GIS category

This QGIS tutorial is part of a series detailing my journey moving from ArcGIS to QGIS and how I’ve relearned familiar ArcGIS workflows. I’ve been using ArcGIS for many years and the move to QGIS has at times presented quite a steep learning curve. Some of what I have learned has come from trial and error, but the greater majority has come from searching forums and other blogs and I try to credit these sources as I go along. Writing these articles is both a personal aide-memoire and a way to cement the new skills I am learning, but if they are helpful to others, then all the better.

QGIS tutorial for archaeologists wanting to create survey grids and export as points to use with a GPS or Total Station.

Creating and Orienting Vector Grids in QGIS 2.18

In this QGIS tutorial I will use a real-life geophysical survey to detail how I use QGIS to create polygon grids, how I orientate them to fit the area of interest and how I export the grid as points to use with a GPS or Total Station system.

In archaeology, laying out a grid before a survey or excavation is an essential part of keeping a fieldwork project organised. Grids can be aligned to real-world coordinates, such the British National Grid here in the UK, or can be on an arbitrary alignment, called a site grid, chosen to best fit the terrain or landscape. A site grid will commonly use a field boundary, verge, fence line or other linear feature as a baseline from which to measure out the grid.

Gridding out, as it’s called, can be done quickly in the field by one or two people using surveyor’s tapes. I’m fortunate to have access to a GPS Rover which can achieve the same result as using hand tapes, but much more quickly and with millimetre accuracy. The other benefit of using a GPS is that the grid can be created in QGIS in the office and transferred precisely onto the field.

QGIS Tutorial Contents

  1. Creating the grid
  2. Orienting the grid
  3. Converting polygons to points
  4. Exporting point layers
  5. How does this workflow compare with ArcGIS?


Merge Multiple Rasters Using Cell Statistics

A simple and elegant way to merge multiple raster datasets in ArcMap is to use Cell Statistics in Spatial Analyst Tools. While there are many ways to merge raster datasets in ArcMap, the most common, Mosaic, can be tricky, as an empty raster must first be created into which the raster tiles are merged. Getting any parameters wrong here could mean a failed merge.

A map I’ve recently created required me to merge several SRTM raster tiles. Normally I’d jump to Mosaic to merge the raster tiles, but remembering this can often be a slow and problematic process, I looked for an alternative method. This search led me to discover that Cell Statistics (Spatial Analyst Tools > Local), a tool I’ve never used before, can merge rasters quickly and without fuss. (more…)

Google Earth Pro now Free!

Google Earth Pro reduced by $400!

Georeferenced LiDAR image of Bigbury Hill Fort, Canterbury, imported directly into Google Earth Pro. On January 30, 2015, Google announced that the Pro version of their Google Earth software would come down in price… to free. Until now, the Pro version would have set you back $400 per year. For those on a tight budget, (or with sense!), this was reason enough to stick with the free version and forgo the extra tools in Google Earth Pro.

I always felt that $400 per year was an almighty rip-off and was happy to integrate the free version within my workflow as far as it could go, and then use other tools where necessary. But what could you do with the $400 Google Earth Pro that you couldn’t do with Google Earth, and why should you now switch? Well, it’s not for higher-resolution imagery, as this is the same across all Google products. But the available toolkit for working with this imagery does increase.

Why a 3D Topographic Model?

dem created in arcgis from contour dataI’ve been asked to produce a walk-through animation of a reconstructed archaeological site that shows the landscape setting of important buildings, and how these buildings constrained the movement of people. Reconstructing the buildings is pretty simple, with lots of reference material available. However, the 3D topographical model of the landscape is much trickier, made worse by not having any digital elevation data, only paper maps with contours.

Drawing contours with height attributes is easy in ArcGIS, but when I was asked to create an animation, I had no idea how to get the GIS shapefile data into my 3d software for animating. I figured there must be a way, and sure enough, ArcGIS has all the tools for converting and exporting a shapefile that can then be opened in pretty much any 3d software package.

Day of Archaeology 2011: Dis Manibus Sacrum

dis manibus sacrum roman gravestone*This post first appeared here as my contribution to the 2011 Day of Archaeology.*

Day of Archaeology 2011: Dis Manibus Sacrum

Lloyd Bosworth: Archaeology Technician, Classical and Archaeological Studies, University of Kent, Canterbury, UK.

My day started like any other day for me. Wake up at 7:30am (ish), make a coffee, put the Today programme on the radio and shamble about the house until the caffeine kicks in. The morning is also when I catch up with the US archaeology blogs that I follow.

Arrival at Work

First order of business is to turn on my workstation and, while that wakes up, make another cup of coffee.