Just posted a new page about an ongoing project mapping industry across Calderdale. Click the map to view.
Just posted a new page about an ongoing project mapping industry across Calderdale. Click the map to view.
I have recently carried out a series of experiments to develop a suitable and effective methodology, using pole aerial photography, to collect photographs of a measured grid marked with targets to produce a photographic mosaic suitable for transcription.
The first issue was to establish the optimum size of grid squares. Initially grid squares 3 x 3m were tried but it was tricky to get the whole grid square in frame. This was more likely if the pole was held off the ground, but this was awkward and not very steady. Grid squares 2 x 2m were tried and found to be easier to capture.
The next issue was how to get the camera centrally over the grid squares. Doing it simply by eye was not very successful. An attempt to use a plum bob was awkward and destabilised the whole rig making it difficult to handle when moving. It also added an unwanted artefact to the images (the string) and may have confused the auto focus.
These sessions used a Canon S100 camera with CHDK running an intervalometer script set to a 10 second interval. This was to allow time to move to the next square and settle the camera movement. At times this was fine but at others it was either to long or to short.
Learning from these tests I built a new PAP rig which includes a wired trigger for the camera and a laser to help with aiming. Again using CHDK, the trigger is a simple circuit that, when a button is passed, puts a voltage of up to 5v across two terminals of a USB cable connected to the camera (the red and black wires, but be careful with the polarity). The camera interprets this as a shutter press. Depending how CHDK is configured this can be one press to trigger the shutter or a double press to first focus and then trigger the shutter. Other options are also available but these are the most useful for PAP mapping. My system uses three AAA batteries to deliver 4.5v. The laser is mounted on the camera cradle and is a cut down red laser pen. As it originally ran on 2 AAA batteries; removing the power source allowed most of the body of the pen to be removed. It now operates via the same control box as the camera.
A 5m Ethernet cable connects the rig to a combined control and battery box containing three AAA batteries. This has an on off switch to prevent accidental battery drain and two push to make buttons. One is wired for 4.5v to trigger the camera and the other 3v for the laser. Laser pointers are not made for continuous operation and so using a push to make switch prevents damage from overheating. As the camera only needs a momentary voltage push to make was again the best choice of switch. The Ethernet cable is ideal as it is fairly stiff and easy to secure to the pole with Velcro ties. It has 8 conductors and so plenty to connect both the camera and laser. Having just a single wire to deal with makes the system more compact and easier to set up and handle. At the rig end the cable is split into two by splicing in two cables. One is a USB cable for the camera with the plug that would normally connect to a computer removed to allow the splice. The other uses a section of USB cable terminated with a 3.5mm mono line plug. The laser has a similar section of cable but with a 3.5mm mono line socket.
The camera is mounted on a simple two part U frame similar to my Kite Aerial Photography rig, but with extra space to accommodate the USB connection to the camera. This also provided space for the laser. Unlike my KAP rig that is made from aluminium this one is made from mild steel bar. It is therefore heavier but if anything that is useful. The U frame is connected to a simple gimbal made by soldering two roller skate bearings into a section of pipe, which in turn is connected to the threaded fitting that came with the pole which is a 5m aluminium painter pole. The gimbal allows the camera to swing back and forward and it is easy to set up the two U sections so that at rest the camera is roughly level. Mounting the laser was accomplished by the discovery that it fitted perfectly in 15mm plastic quick fit plumbing pipe. This allowed the use of a 15mm pipe clip to secure it to the frame which ensures that it stays in alignment with the camera.
In practice this set up is far superior. The pole is placed on the ground and tipped over a grid square and the laser button is pressed. The pole is then adjusted until the dot is about in the centre. The shutter is then triggered with a double press of the shutter button. The pole is the moved to the next square and the process is repeated. This is much faster and photographs with only partial coverage of grid squares are eliminated as are out of focus images.
To support the Meerstone Community Archaeology Manual I have over the last 6 months or so created a number of tutorial videos on surveying and GIS, and added them to a new YouTube channel.7
I have had to take on all the roles that you might expect from video production. Writer, graphic artist, cameraman, soundman, editor, director, producer, and presenter. Not easy, especially as I have had a budget of zero. It has been a huge learning curve but with each one I feel that the quality has improved.
Online videos often fall into two categories: low quality (low res and poor sound), or really slick HD (think bright, loud, flashy and dynamic). I don’t have the skills, time or equipment to complete with the HD guys but I have tried to produce videos that are at a good resolution, have clear audio and that contain concise easy to understand content while also being visually interesting. I’m not going to be the next Spielberg but I think that I have hit the middle ground between the two extremes of online video content.
Look out for the use of standardised titles and credit sequences, channel idents and use of music.
You can also view a video version of this post
Having accidentally getting involved in community archaeology, running a successful project at Middleton Park, Leeds, that won a highly commend in the British Archaeology Awards, I have gone on to produce the Meerstone Community Archaeology Manual as a way to share knowledge that I have gathered over 25 years as both an amateur and professional archaeologist. I have written a summary of my unconventional route into archaeology here.
Because I carried out my own fieldwork for many years with minimal resources, and, more recently working with community groups and local archaeology societies, I have seen how a lack of knowledge, equipment and often confidence can impact on the success of project.
This is probably a result of my northern working class roots, but I am a great believer in giving people the opportunity to access information and giving them the chance to produce high quality work that they can be proud of. I have, rather tongue in cheek, suggested that the manual is a stepping stone on the road to self enlightenment, encouraging and enabling intellectual access to the same resources as professional archaeologists. Joking aside I have taught enough people to know that even the most complex archaeological tasks can be done by most people with the right guidance. There is a great quote attributed to Einstein that says “if you can’t explain it simply to a six year old then you don’t understand it yourself”. Long before I found the quote I had realised the importance writing accessible text. Breaking processes down into smaller stages with clear step by step instructions works really well. Scoring these stages lets people understand the difficulty of a task before they begin and providing check lists and flow charts builds confidence that they are doing it right.
I have to confess that I use these check lists and flow charts myself. Commercial archaeology is often rushed and it is easy to forget a small but key bit of information, for example, when working alongside excavator drivers who are on a tight deadline and sometimes see archaeologists as an inconvenience.
Use of open source and free software is at the heart of the methodologies. Having seen how projects can struggle because of a lack of access to effective software this has been at the core of the project from the start. Learning to use specialist software such as CAD and GIS can give people transferable skills. This can have long term benefits if volunteers are able to have continued access to the software. Although a much abused term these are “legacy skills” that can be taken to other projects. I have seen local archaeology groups move from projects run be a professional archaeologist to running their own projects using their acquired skills.
The manual is open content which means that the content is not fixed; it is constantly being revised and added to. I have described it as a bit like Wikipedia but with an editor. Wikipedia is a great socially inclusive concept allowing anyone to add information, but having no one to check and correct facts is a weakness. Anyone can offer material for the manual or request improvements or new content. I did have a vision of it becoming a community resource with many authors but that has been slow to take off. Open content offers a flexibility not possible with printed books and with the spread of tablet computers and eReaders, ebooks are a portable alternative to traditional books. Other advantages of the ebook format include the ability to include more illustrations, and they can all be colour images. The manual is deliberately image rich. I am a visual thinker and find that well thought out diagrams, flow charts and photographs can provide explanations that would be overly complex if provided simply as text.
Visit the project’s Wiki to find out how to get a copy and see the latest news about the project and see a sample copy.
I haven’t always been an archeologist, and how I became one was far from a conventional route. The following is a summary of my life journey from school until now.
I left school with very few qualifications after to missing almost 2 years due to the aftermath of Glandular Fever. I went on to study building at the local college but again due to ill health was unable to finish the course. At the time this was described as post viral debility. I now know that it is actually chronic fatigue syndrome, which is often linked to the Epstein–Barr virus, responsible for glandular fever. As a result of my poor qualifications my twenties were mostly spent in low paid work. This was interrupted again by my health. This time a different set of doctors and a different diagnosis. I now apparently had an arthritis condition, which amongst other things was responsible for my continuing chronic fatigue. I was finally correctly diagnosed with chronic fatigue syndrome about 8 years ago.
I have always had a strong general interest in history in the broadest sense. Some of what were to become my special academic interest have their roots in the books from the library that I read when I was off school. My explorations in my early 20s got me out and about to visit sites that I had read about, and gradually I began to find that books I was reading did not quite agree with what I was seeing. That set me off to start both recording sites and researching them in the county archives. I taught myself both survey and research skills.
Fast forward to my mid 30s and I was still having problems with my health, but decided that I really should try to improve my qualifications to improve my job prospects. My return to education after 15 years, initially doing part-time evening classes at local universities, but then making the big step of going full-time was quite a journey and I rapidly realised that my interest in history had more of a focus on archaeology.
Gaining a first class degree and winning three awards for my dissertation was unexpected. Next a masters degree and then a PhD, during which I started my own business. Self employment is a choice that many with long term health problems make and it certainly allows me to work around my issues, most of the times. Currently like many archaeologists I am finding work thin on the ground. Perhaps fortunately this has coincided with a downturn of my health and the revelation that as well as chronic fatigue syndrome I also have Aspergers Syndrome, a higher functioning form of Autism. I have discussed this in my book A Different Perspective which is filled with my kite aerial photographs.
These health low points are often cyclical and will hopefully improve soon. Keeping busy physically and mentally is an important part of managing long term health conditions and recently I have put all of my energy into writing the open content Meerstone Community Archaeology Manual. This has developed from a community archaeology project that I ran in Middleton Park, Leeds, that won a highly commended in the British Archaeology Awards. The manual is a colossal project that currently stands at nearly 80,000 words in 378, A4 pages and continues to grow. Writing this has been very therapeutic and kept me pottering along when I could have just given up and felt sorry for myself. That’s just not who I am.
So its not been an easy journey, far from it; and it wouldn’t have been possible without having the right support at key times (you hopefully all know who you are). Naturally there have been many who have not provided suitable support. I wonder if those teachers who wrote could try harder on school reports ever considered that I might had done better if they had tried harder? Despite the odds being against me my achievements have been beyond my expectation, but I’m not finished yet.
Note that I have so far avoided the D word Disability. In the UK you are considered disabled “if you have a physical or mental impairment that has a ‘substantial’ and ‘long-term’ negative effect on your ability to do normal daily activities.” When you look at this closely it becomes a wonderfully fluffy definition underpinned by the words negative and normal. Looking out from the inside normal is what you experience everyday and will usually be very different to the normal experienced by others. Negative is a concept that relates more to those looking in rather than those looking out. Something is only negative if you make it so.
For people with long term healths issues Disclosure, the other D word, is a very difficult dilemma. Tell people you have complex long term health issues and you will frequently experience negativity or a smotheringly suffocating level of assistance. There never seems to be any balance. Some will assume that you cant do things and therefore won’t give you the opportunity. Others assume that you need constant help. Please, that is just patronising.
The politically correct, overly empathetic, who talk about ability rather than disability, and a condition rather than a disorder can be a real pain. They rarely listen, too busy falling over themselves trying to “help” you. Others will misinterpret your behavior as they have totally ignored what you have told them about you condition.
I have chosen not to hide my health issues. By making this disclosure I am not looking for sympathy or empathy. Personally I have no time for those who wallow in self-pity and you wont read a blog from me that documents every bad day I have. What I want to show is that I have worked hard and my achievements are not insignificant.
I have a good portfolio of work and publications which show what I can do. I sometimes have to do things in a different way to others or over a longer time period but the results will be, at the very least, to the expected standard.
App Inventor started as a joint project between Google and MIT in 2010, but dropped by Google at the end of 2011, this project is now being run entirely by MIT. The system is designed to let non programmers build android apps, without ever seeing a line of code. It achieves this through a simple concept using two screens. The first which opens in a web browser is where you set out the components that you want in the app, buttons, text boxes, labels and images.
You then open the blocks editor and this is where you give life to the components and other behind the scenes processes. From the blocks editor you can either connect to your android device or open an emulator. This lets you see how the app is working as you build it and test it. The blocks editor is the most remarkable part of App inventor. Here you assemble your app from a set of jigsaw pieces (blocks) linked to your components. You can set up math, logic, text, and other actions by joining blocks. These jigsaw pieces can only be connected to other components where the designated tasks will work together.
As a visual thinker I have found this to be such an easy way to build and test simple apps. After following one tutorial on the app inventor web site I was able to build my own, a simple calculator to give the height of a building by measuring a distance from a wall, an angle up to the top and down to the base of the wall. It probably took me just over a day to get it working, and equally important, looking good. By the end of the week I had four similar apps, all useful for archaeological projects.
These are Building Height Calculator, previously mentioned, Calculate 3,4,5 an app to aid setting out at right angles with tapes, Level Reducer converts spot heights to correct height AOD therefore removing the need to calculate heights afterwards. Scale Calculator returns the scale distance in cm and mm of real world distances in m, at a specified scale. Having an app make these calculations automates the process, compacts the process, and reduces the chances of errors. I think that for amateur archaeologists they also deliver confident figures to those unfamiliar with the calculations.
The apps have been packaged into one called Archaeology Field Calculator which is now being tested on different devices and will probably be included in the next version of the Meerstone Community Archaeology Manual which should be released in the next month or so.
Just a few pros and cons
The next installment in my Nexus 7 tests has been a proper field test, collecting more meaningful data. For this test, as before, using a Qstarz GPS818X bluetooth GPS receiver running through the Bluetooth GPS Provider, points were recorded on the tablet using the Droid2CAD app. The same features were recorded with a Garmin Geko GPS in WAAS enabled mode. The bluetooth GPSs was able to acquire a differential lock and the accuracy was under 3m, getting as low as 1.8m. The Geko also acquired a differential lock. The accuracy of each point was not recorded but was between 6 and 2m.
The drawing above shows the Qstarz points as triangles and the Geko points as circles. The results are close but not exactly the same. One reason is that the feature recorded, an old coal shaft, was covered in heather which made it difficult to judge where the edge was. The difference is between 1 and 4m but could be simply put down operator error, not walking the same route around the shaft mound. In the center is a roughly square area of different vegetation which is interpreted as the position of the shaft. This should have been very similar, however it is not. The shape and proportions are similar but there is a slight difference in size and, as can be seen above, the bluetooth results are offset by approximately 3m. Plotted against Google Earth satellite imagery the geko points are a closer fit than the Qstarz points. In order to explore this difference further and get a better understanding of the inherent errors my next test will be on a site where I can more accurately record the same detail using different GPS hardware.
This took place on a local sports field recording points around a rugby pitch.
The points plotted above over a 5m grid represent tests on two different days following the same methodology. On both days the points were recoded with the Nexus 7 and Garmin Geko. Both device achieved a differential lock. The pale blue triangles are the Geko points and the diamonds were recorded with the Nexus. These represent points from the Qstarz GPS818X bluetooth GPS receiver with a set, coloured red, coming from the on board GPS. The latter without a differential lock. All the points have a similar clustering, with occasional outliers. The Geko reported accuracy from 6m to 2m. The Nexus with Bluetooth GPS quoted between 3.1 and 2.1m. The internal GPS gave an accuracy of 6-12m.
My analysis based purely on observation of the plot is that there is little difference between the receivers, with perhaps a slightly tighter clustering from the Gecko. This despite the differences in the reported accuracy.
Having recently bought a Nexus 7 I have been keen to explore its suitability as a tool for archaeology. First a test of its mapping potential using GPS.
For this test points were recorded on the tablet using the Droid2CAD app. First 100 points were recorded using a Qstarz GPS818X bluetooth GPS receiver running through the Bluetooth GPS Provider app. 100 further points were recorded with the Nexus 7s own GPS. All the points were recorded in the same location; indoors sat on the sofa, just to challenge the sensitivity of the receivers. The data sets were recorded on subsequent evenings over an hour or so.
The graph above shows the range of accuracy readings. The scale on the left is showing the accuracy in meters. The top red line is for the on-board GPS and the lower blue line is for the bluetooth GPS. The difference in quoted accuracy is dramatic, however when compared to the plot of the latitude and longitude below the results are not so different. The circles are from the bluetooth GPS and the triangles for the on-board.
Both sets of points have a similar clustering within a 10m radius, although the actual center of this area is out by about 5m west and 2m north of its true location. This is likely to be an issue with converting the native GPS WSG84 coordinates to OSGB1936 in QGIS. Within that 10m circle the Qstarz GPS818X has 49 points with a tight cluster of 15 readings within a 2m diameter circle. In contrast the on-board GPS has 73 of its points in this area with no apparent clustering.
There are many instructions for DIY light tents online which are based around cardboard boxes. Naturally these don’t fold flat for storage in a drawer. This model not only folds for storage, being folded flat also makes it very portable. This means that you can set it up anywhere. It is an instant pop up studio where ever and when ever you want it. No need for flash guns (strobes) (although you could still use flash with this tent), all you need is suitable lighting such as desk lamps or spotlights.
Cut 5 – 30cm x 30cm squares out of mount board. Naturally you can make these any size that you want but this size will probably suit most uses. Take 3 of them and cut windows leaving a border of about 4cm, glue drafting film to the inside. Alternately you could use tracing paper, which is cheaper and easier to find. This will act as a diffuser to soften any light entering from outside the box.
Use the tape to join the two boards without windows. They will form the floor and back of the tent. Tape on both sides but make sure that the boards can fold flat as shown above. Join the window boards in a similar way ensuring that they can still fold flat. Making a Z or W fold (see below) works better; i.e. one board goes behind and one goes on top.
Add small pieces of Velcro to the edges to hold the sides in place. Glue and staple them in place. Don’t add Velcro to the side that joins the back solid panel to the top window.
Finally add a sheet of paper down the gap between the back panel and the top panel, clip it in place and allow it to curve across the bottom sheet (see below). This prevents shadows. Alternately you could use a piece of fabric choosing a colour to suit your subject. The two most common colours used are black and white.
Once you have set the object to photograph in place, shine spotlights through the most appropriate window, or windows to light it (see lighting tips below). Here two clip on spots are fastened to a frame made from an old shelf unit. Be careful when using lights like these close to the light tent as they can get quite hot.
By unfastening the Velcro and folding the boards the light tent packs flat for storage until you need it again.
You don’t need a fancy or expensive camera to use a light tent. Many compact cameras have setting that will let you alter the white balance for artificial light; they will also allow you to disable the cameras flash. Lighting an object from above or the side or even both is usually more pleasing than using the built in flash. If you are using spotlights its a good idea to keep your camera as still a possible to prevent blurring. You could stand it on the same surface as the light tent or you can use a tripod. If you don’t have a tripod but find that you want the camera a bit higher you can stand it on top of a couple of books. Naturally if you have flash guns (strobes) you can use these to light through the panels.
To get professional looking results you may need to edit your photographs to strengthen the background. Usually this will be adjusting the brightness and contrast to make it a brighter white or blacker black.
This tutorial assumes that you know what CHDK is and have successfully identified your firmware version and loaded the correct CHDK build onto your cameras memory card (for the S100 see here and look out for the link to a quick step by step guide). I have also assumed that you will be able to work out how to scroll up and down the menus and select options by pressing FUNC SET. It is quite intuitive.
Different CHDK builds for this and other cameras may look slightly different but these instructions should still help you get you started.
Once you have set up your card lock it and put it back into the camera. Now switch it on by either pressing play or the on/off button. You should then see the CHDK splash screen below.
This will disappear and your camera will function normally. Press play and you will see alt at the bottom of the screen. CHDK is now running and capable of overriding the cameras settings.
CHDK allows you to set and control many parameters and if you loose track of what you have done and want to clear the settings go to CHDK Settings and scroll down to Reset Options to Default. With such a complex set of options this can be quicker and easier than trying to find a wrong setting that is causing the camera to misbehave.
To override the camera settings select Enhanced Photo Options in the main menu
Set Disable Overrides to NO and then set any options that you want. Here I have only selected Override Av (i.e aperture) and set the value to 2.05 which is the maximum setting that it will allow letting maximum light get to the sensor. Your preferences may be different. With the camera set in Tv mode the speed and ISO can be set as usual without going into CHDK.
Press menu to exit and then press FUNC SET to open the Script menu.
You will now see your selected script at the bottom of the screen and can set any variables. In this case the interval has been set to 2 seconds. Press back and then the shutter button to start the script. The script will run until you turn off the camera, or the card fills up, or the battery gives up.
This script will work for both KAP (kite aerial photography) and PAP (pole aerial photography).