Finding Archaeological Sites from the sky using high-tech advances in archaeology

In recent months, news feeds have been erupting with stories of “Lost Maya Cities discovered using LiDAR”, “revealing the secrets of Stonehenge using LiDAR”, “LiDAR uncovers ancient city near Angkor Wat”, and the popularity of “space archaeologist” Sarah Parcak, but this technology is not limited to finding the remnants of “lost civilizations” in far reaching corners of the globe. LiDAR is used by archaeologists in Alberta to assist in the locating of potential archaeological sites that are threatened by development.

Figure 1. Marching Bear Effigy Mounds Lidar Imagery (Wikimedia Commons)
Figure 1. Marching Bear Effigy Mounds LiDAR Imagery (Wikimedia Commons)

Light detection and ranging (LiDAR) is the process of mounting a laser on an aircraft and bouncing light pulses off the ground and measuring the time it takes for the laser to return. The process can take 2000-5000 measurements per second and makes the surface appear treeless, revealing surface features that cannot be seen using simple satellite imagery or aerial photos (Figure 1). However, using LiDAR to find archaeological sites in northern Alberta is not as easy as it can be in other parts of the world. LiDAR is great for identifying building structures, walls, and other features common of archaeological sites in other parts of the world. In northern Alberta these features are absent from Indigenous archaeological sites. To study the human history of northern Alberta prior to European contact we have to look at the landscape and identify landforms that would have been suitable for camping and hunting activities.

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Figure 2. Satellite imagery of ridge overlooking marsh
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Figure 3. LiDAR hillshade of the same ridge

In the above images, the first image is a satellite image of a ridge where we found an archaeological site (Figure 2). With just satellite imagery the area appears to be predominantly flat which is not a good area to camp or hunt. This is because the area would be thought to be poorly drained and with limited visibility of the surrounding terrain. When using LiDAR imagery (Figure 3) we notice there is a complex of distinct hills and ridges that would be ideal for making camp.

This technology has revolutionized the process of finding archaeological sites in Alberta and is revealing more about the history of people in the boreal forest. The ability to pinpoint the best landforms without having to do extensive on-the-ground survey has greatly increased the inventory of sites found in northern Alberta. This benefits our clients who will pay less money for the survey of their developments and we can make more accurate predictions about site locations which allow them to modify their developments to avoid potential sites.

Side-Notched Projectile Point

We often post images of beautifully crafted tools such as the besant point from FcPu-11 or the siltstone knife from Buffalo Beach but not every tool we find is a “work of art.” This week’s photograph is of an “ugly” artifact we found in 2016 when undertaking an HRIA for Sundre Forest Products. The site was found on a terrace overlooking the confluence of two tributaries to the North Saskatchewan River. The artifact is a side-notched chert projectile point similar to the Prairie or Plains side-notched typology. The point is asymmetrical with one edge being a rounded convex shape and the other an undulating edge with an angular shoulder. The tip of the point is broken off which is common of the projectile points we find and is likely the reason the point was discarded. While aesthetics can add to the function of a projectile point this artifact demonstrates it was not necessary. The idea that it doesn’t matter how it looks as long as it works was alive in the past as much as it is today.

Introduction to CRM Part 5: Reporting

Once we have surveyed our targets and evaluated any sites we have found, it is time to return to the office. All of our notes are taken on an ipad in the field. Now all we have to do is export our notes into a database which eliminates the hours spent on data entry.

Note taking is extremely important for archaeologists (Figure 1). The notes supply researchers the context of the artifacts. In this case context means the precise location of the artifact and it’s association with other artifacts and landscape features. This helps researchers determine such things as the relationships between artifacts on a site, it’s position in time and space, and even how it is related to different archaeological sites (Figure 2). Without notes and proper excavation methods, the context in which the artifacts were found is lost forever, and the artifacts have little scientific or interpretive value.

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Figure 1. Eric taking notes on an iPad that will later be used to interpret the site.
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Figure 2. An artifact in it’s original context found at an historic site.

We also catalogue all of the artifacts that were collected in the field. We take measurements, weights, and note details such as material and artifact types, and enter them into a database (Figure 3). This along with the site notes gives us the information we need to write our reports.

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Figure 3. Madeline is weighing an artifact.

In the final stage of the Historic Resources Impact assessment, we compile a report of all the work that we have done and submit it to our clients and the government. The report identifies which developments need to be modified to avoid impacting significant archaeological and historic resources. The site information is included in a government database of all the sites in Alberta as a reference for future industry development as well as researchers. This minimizes the impact that our clients have on Alberta’s history while preserving the past for future research and education.

Sometimes you just can’t win!

Digging in the forest we are always encountering tree roots. It’s a great test when you miss them all. Most days your shovel is sharp enough that you hardly notice the roots as the shovel blade slices through them. Sometimes you have layers of roots, which work as a group to form a wall. You can “smash” through them with a bit of effort, one root at a time. And then there are days like pictured here! Your shovel just won’t go through or you don’t have the energy to “smash” through them, so you have to break out the big guns! I like to carry a folding saw with me in my vest, so roots like these won’t get the better of me! Unfortunately these ones did. So I just dug around them.

Introduction to CRM Part 4: Evaluating a Site

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Figure 1. Positive shovel test that contained lithic debitage.

When we identify a site, we conduct further evaluative testing to determine the type, character, and extent of the site. This is done according to government guidelines, and depends on the type of site, and the type of landform. If the landform allows for it, testing occurs in each cardinal direction or in a grid. Some sites are found on ridges or point terraces, and so in these cases, it is not possible to test in all directions (Figure 1).

Tree Time’s standards are that there must be three negative tests spaced at most 10 m apart in each direction from any positive. Sometimes additional tests are required in order to determine the significance, the size, and type of the site. For example if none of the evaluative tests were positive, further testing might be done at closer intervals to better determine the significance of the site. In addition to rigorous note taking, we also map and photograph the site (Figure 2).

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Figure 2. Vince taking notes at a site.

The evaluation of the site is an important step for two main reasons. The first is to enable the government to maintain an accurate site database and to better inform future researchers of the size and type of sites are in the area (Figure 3).

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Figure 3. We are evaluating an historic site by flagging artifacts with red flagging tape.

Secondly, in this stage we determine the extent and significance of the site. If a client decides to avoid the site, delineation allows us to more precisely buffer the site. This is important because it allows the development to occur as close to the original plan as possible while still avoiding impacts to the site. In addition, if a client chooses to mitigate their impacts to the site through excavation, a more detailed evaluation of a site allows us to better predict the productivity of the site, and to render cost estimates of any mitigation work more accurately.

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Figure 4. Buffer flagged around the site with orange flagging tape.

Once we have surveyed our targets, evaluated any sites we have found, and have finished our notes, it is time to return to the office (Figures 5 and 6).

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Figure 5. Reid is finishing his notes before we move onto another target.
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Figure 6. After a long cold day, Brittany heads back to the office.

Introduction to CRM Part 3: Archaeological Survey

Using information compiled in the office, the next step of an HRIA is to leave the comforts of home behind and to venture into the field. Although there is a perception of archaeologists working at large excavations, often dressed in khakis and maybe wearing a fedora, archaeological survey is the most common type of field work in the CRM sector. So for now, we will focus on archaeological survey and discuss archaeological mitigation in an upcoming blog.

The purpose of an archaeological survey is to visit the high potential target areas we identified in our background research and GIS review in order to see if there are any historic or archaeological sites. We travel to these high potential locations using various means of transport including trucks, ATVs, Argos, the occasional helicopter for the most remote locations, and a lot of hiking (Figures 1 and 2).

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Figure 1. Teresa and Vince in an Argo travelling to target areas.
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Figure 2. Archaeology happens in all weather as Teresa and Brittany hike in snow to our target areas.

When we arrive at these locations, we use experience and expertise to determine if the landform has potential for archaeological and historic sites. For example, is this spot flat and dry? Would we like to camp or hunt from here? High, dry areas, and spots that have nice views are often tested. In fact sometimes we identify a site in the exact spot where we dropped our gear for lunch, as we naturally tend to stop on the best part of the landform (Figure 3).

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Figure 3. Our gear placed at a positive shovel test, flagged with red flagging tape.

 

The most common method of subsurface sampling that we use is screened shovel tests (Figure 4). This means we dig holes about 40 cm square and 30 to 40 cm deep and screen all of the sediment in portable screens. If there are any tree throws or surface exposures, we also conduct opportunistic examinations of these for artifacts (Figure 5).

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Figure 4. Matt is shovel testing.
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Figure 5. Picture of a tree throw that allows for opportunistic sampling.

There are several different sampling strategies that we use, these include systematic, semi-systematic, and judgmental testing. Systematic testing is the term we use when we place tests using a set interval, for example digging a test every 10 m along a landform. For judgmental testing we do not use a set interval instead we place shovel tests on the best part of a landform based on our past experience and conceptual models of how people lived on different types of landforms. Finally, semi-systematic testing is a combination of the previous two. For this method we place tests on the best locations of a land-form while trying to maintain a certain overall density of testing.

The shape of the landform helps determine what type of sampling strategy to use to test a target. A long uniform ridge might be better suited for hybrid or systematic testing, while a hillock might be more often tested in a judgmental manner (Figure 6).

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Figure 6. Brittany testing a target using a semi-systematic strategy.

If the tests are negative, then we write our notes and move on to another location to survey. However, this does not mean that we can definitely say there is not a site at the location. Negative results only reduce the chance there’s a site at a location. To be 100% sure, we’d have to do a lot more excavation (Figure 7).

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Figure 7. Although a nice area near water, we did not identify a site here.

On the other hand when we do identify a site, then we stay at the location to undertake further evaluative testing (Figure 8).

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Figure 8. Vince is very happy after identifying a site when he found a point in a shovel test.

Introduction to CRM Part 2: Development Screening and Project Planning

The first step of a historic resources impact assessment (HRIA) happens in the office. Once we have the plan for a development, we need to assess whether the footprint will impact any recorded sites or if it has the potential to impact any unrecorded sites. We use our experience and knowledge of archaeology, GIS data, and databases of recorded sites in order to identify high potential areas that might have any archaeological and historic resources (Figure 1). Although this stage of archaeology does not capture the imagination of the public and isn’t very exciting or glamorous, it is the most important part and the foundation of our work.

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Figure 1. Corey is targeting areas of high potential using QGIS.

High potential areas vary by region, depending on the geography and the history of the area. Generally areas that people would camp or travel through are considered high potential; these include well-defined landforms and areas near water. We also take into account the environment of the past. For example, shorelines fluctuate, and rivers and streams may change course or dry up. Areas near water generally have higher potential because they were used as a method of transport, offered fishing opportunities, and, of course, they were also a source of fresh water (Figure 2).

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Figure 2. View from an archaeological site looking towards a lake.

Sometimes a development plan will conflict with a previously recorded site. In this case, we can recommend either that the development plan be changed to avoid the site, or that impacts to the site be mitigated by excavation. If there are no recorded sites in the footprint, but there are areas that we think are likely to have sites, we recommend field survey. Using GIS data and the research that we have complied concerning the area around the developmental footprint, we create targets of high potential areas to survey in the field. The next step takes us out of the office and into the field.