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ProbeCorder: Pen-based Computing for Sediment Profile RecordingJames A. Zeidler |
Introduction
Systematic subsurface testing procedures are an
increasingly necessary solution to the problem of discovering archaeological
sites that are either deeply buried or obscured by dense vegetation. They are
also commonly used in comprehensive significance assessments of archaeological
sites in which extensive and rapid testing of site boundaries, site depth,
stratigraphic integrity, and feature content is desirable. Soil scientists and
geomorphologists must also rely on them for the study of site-specific
sedimentary sequences and regional landscape evolution. Such procedures are
extremely labor intensive since they often involve repeated, closely spaced
probing by means of shovel-testing, postholing, bucket augering, deep coring,
or back-hoe trenching. They also generate enormous amounts of standardized
paper forms that require additional steps of postfield data integration and
digital transformation before final reports can be prepared. These data usually
include a variety of formats including: gridded sketch maps of probe locations
within a survey unit or site; lengthy verbal descriptions of sediment profiles;
rapidly executed drawings of sediment profiles; artifact provenience lists;
sediment sample lists; and comprehensive archaeological site records. Much of
this data is never utilized to its full potential due to the high cost and
labor intensity involved in the manual conversion of paper-based field data of
variable legibility into a suitable electronic database format. The sheer
volume of archaeological and pedological information normally recovered during
intensive subsurface testing programs has created a need for maximizing
efficiency both in field data recording and in post-field data processing and
integration.
In order to reduce these costs, field data collection procedures (including probe data recording, site recording, sketch mapping, and field specimen management) should be as efficient as possible, preferably involving the automated recording of field data as it is being collected. A number of solutions to this problem have appeared in recent years, including the development of software programs for use with small, handheld data collectors for routine electronic recording and logging of archaeological field data (see, for example, F. Schneiderman-Fox, and A. M. Pappalardo, 1996, A Paperless Approach toward Field Data Collection: An Example from the Bronx. SAA Bulletin 14(1): 1, 18-20). Handheld data collectors have been in use for years in a range of professions involving outdoor fieldwork and allow simple data logs to be recorded for subsequent downloading to a relational database system running on a desktop PC. While extremely useful in certain contexts, however, they tend to suffer from limited storage space and display capabilities. A rather unexplored area of automated field data collection in archaeology, and one that is increasingly being pursued in other professions, is the application of portable, pen-based computer hardware and "mobile GIS/GPS" software. As we shall see, this platform is particularly well suited to sediment profile recording for archaeological and pedological purposes.
A Primer on Pen-based Computing
and Mobile GIS/GPS
Pen computers (also known as PC tablet computers) function as handheld,
battery-powered "electronic clipboards" for maximum portability and rugged
outdoor use. They operate much like a laptop or notebook computer with the
extra advantage of an electromagnetic digitizer and pen stylus for sketching
and single-handed data entry directly on the computer's screen. Like any
notebook computer, they run Microsoft Windows 3.1tm or Windows
95tm operating system and compatible software packages. In addition
they also run the Microsoft Windows-for-Pentm pen extensions. These
are the electronic pen drivers installed by the manufacturer that permit pen
gestures, inking, and handwriting recognition in any Windows-compatible
Microsoft software program. There are several pen computers currently on the
market and they vary somewhat in their degree of ruggedness and user
friendliness. In general terms, the more rugged and portable the platform, the
less user friendly it will be (e.g., no keyboard, no internal floppy drive,
smaller screen size, etc.). However, many of these computers make up for their
internal limitations through add-on peripheral devices that can be attached
when the machine is not in portable field mode and permit operation as a fully
functional desktop PC.
Common brand names and models for the rugged varieties include the Huskytm FC-486, the Telxontm PTC-1184E, the Kalidortm K2500, the Badgertm GT-486N, and the Teklogixtm TKX-3000. (The latter two are actually rugged notebook computers with pressure-sensitive touch screens and an optional pen interface.) Less rugged but still fieldworthy brands and models for outdoor work include the TelePadtm 3 and the Fujitsutm Stylistic series. All of these models currently operate on a 80486 microprocessor, but clock speeds range from 33 to 100 MHz. Eight MB of RAM is now standard and is usually upgradable to 24 or 36 MB. Internal hard drive capacity ranges from 170 to 525 MB as standard features but most systems are upgradable. Hard drive capacity is also expandable through standard PCMCIA technology (flash disks), and all of these systems have internal PCMCIA slots offering different combinations of slot types. Internal GPS capability is also added on in this fashion (e.g., the Trimble Gold Cardtm). Pricing on these pen computers ranges from $2,000 to $6,000 depending on brand name, and power, speed, and hard drive configuration. As with PC hardware generally, available configurations are constantly changing and new features are frequently added.
Several commercial off-the-shelf (COTS) software packages exist for the pen-based hardware platform, most of which are aimed at GPS data collection and map display. Some packages offer separate software development kits, which permit the end-user to design customized electronic forms for standardized field data recording, including digital photographs and inked sketch maps or drawings (e.g., Geofirma's Mobiletm and Designertm software). One of the most powerful of these pen-based programs is PenMetrics' FieldNotestm mobile GIS/GPS software (currently in version 4.0). This program brings much of the functionality of Geographic Information Systems to the pen-based computing platform by allowing the user to store, analyze, and query spatially referenced attribute data in the same environment. Maps (both raster and vector) and imagery can be imported from a variety of formats, and drawing overlays can be created and saved in CAD format. An integrated Global Positioning Systems module is available for GPS data logging and mapping. The FieldNotes program combines efficient field data recording with powerful graphic display and storage capabilities that effectively integrate GIS, GPS, and CAD functions. A software development module (FieldFormstm) allows the creation of customized field recording forms such that detailed attribute data can be recorded, plotted, and georeferenced in a previously defined map coordinate system. Pen-based mobile GIS computing provides substantial benefits for field data collection. By automating the recording and data storage process, considerable gains can be made in efficiency and accuracy when compared to traditional methods of field recording with paper forms and penciled sketch maps. Routine field data collection and validation, inventory management, and field mapping can all be carried out quickly, easily, and accurately for subsequent conversion to a desktop GIS, CAD, and/or RDBM system. Table 1 outlines some of the chief advantages of pen-based mobile GIS computing.
Table 1. Benefits of Pen-Based Mobile GIS Computing
ProbeCorder: A Cost-Effective Solution
for Sediment Profile Recording
As a means of partially mitigating the high cost of subsurface testing in
archaeological field investigations, the Tri-Services Cultural Resources
Research Center of the U.S. Army Construction Engineering Research Laboratories
(Champaign, Ill.) began developing an automated pen-based computer program,
entitled ProbeCorder, for more efficient field collection, integration, and
storage of subsurface probe data. The project was initiated with funding from
the Legacy Resource Management Program in support of the army's broader goal of
establishing cost-effective, standardized methodologies for the collection,
storage, and retrieval of cultural resource information on Department of
Defense landholdings. The project is currently sponsored by the U.S. Army
Environmental Center (Aberdeen Proving Ground, Md.) which is providing
technology transfer oversight and technical support within the Department of
the Army.
ProbeCorder is a pen-based software tool designed to maximize the logistical efficiency of subsurface testing by automating the routine collection, integration, and storage of probe data in the field. The program is written in Microsoft's Visual Basictm programming language and provides a user-friendly Windows environment for the complete field recording of subsurface testing data. It consists of a series of Windows dialog boxes, which record administrative and locational references, sediment profile descriptions, and artifact/feature content for each probe within a user-defined survey unit and sampling geometry. The system permits a small sketch of each sediment profile to be drawn and saved as a bitmap file. Each sedimentary unit identified in the profile can then be fully described in terms of its maximum depth, texture, horizon, structure, boundary, and Munsell soil color. All field data are then stored in an internal relational database, which uses Microsoft's FoxProtm database format with full querying and report-generation capabilities. On-line help is available through a series of context-sensitive Help screens located on all of the principal dialog boxes. The system has now been successfully tested on five different pen computers including the TelePad SL, the TelePad 3, the Telxon PTC-1184E, the Husky FC-486, and the Kalidor K2500.
ProbeCorder has been developed to run in two modes. It can function as a stand-alone program accessed directly from the Windows Program Manager, or it can function as an application module within the mobile GIS software environment of Penmetrics' FieldNotes (versions 3.1 and 4.0). Subsurface probe recording can be carried out either for site discovery purposes within a predetermined survey unit or transect, or for site assessment purposes within a known archaeological site. The arbitrary "survey unit" and/or the culturally defined "site" then become the basic administrative and spatial contexts within which individual probes are recorded (Figure 1). In either case, a user-defined sampling geometry can be established within the FieldNotes environment, and an annotated sketch map of the tested area can be created in the same way that gridded sketch maps are utilized when recording in a paper format. With FieldNotes, however, the resulting electronic sketch maps can be directly exported to CAD format for subsequent modification and enhancement on a desktop CAD system. By creating drawing overlays of all survey unit, site, and probe locations on a background map of the larger study area, all of the associated ProbeCorder databases are automatically georeferenced and ready for export to a desktop GIS.
Recording Sediment Profiles
Module 1: Survey Unit Record. The Survey Unit Record screen allows
recording of subsurface probes within an arbitrary spatial unit or quadrant for
site discovery purposes. It provides basic administrative and locational
information about the survey unit such as Survey Unit number, size, UTM
coordinates of center or SW corner, and user-defined sampling geometry. Probe
type can also be identified and a running summary is maintained on the number
of positive probes, negative probes, and total probes executed. If a site is
eventually identified within the Survey Unit, the corresponding site number can
also be recorded and stored in the Survey Unit data table. Figure 2 illustrates
a blank Survey Unit record dialogue box. The UTM coordinates can be obtained
either from a stand-alone GPS unit or from GPS software and hardware embedded
in the pen computer. In either case, however, the UTM coordinates must be
entered on the screen manually with the pen stylus or keyboard.
Module 3: Probe Information. The Probe Information screen permits recording of administrative details on each probe, including its corresponding survey unit or site, probe number, recorder, date, and provenience number if field specimens are recovered. Once the probe has been completed, the probe outcome (positive or negative) can be selected in the Results box. The Probe Information screen is the entry point and exit point for conducting the sediment profile description. The probe description procedure is initiated by clicking on the Profile and/or Content buttons in the lower right corner of the screen. By selecting "shallow profile," a sedimentary column up to 1 m deep can be described. For deeper probes carried out by augering or coring, the "deep profile" option can be selected to permit sketching and full recording of sedimentary columns up to 20 m in depth. Figure 3 partially illustrates the Probe Information screen, which is superimposed by the cascaded Profile and Deposit Entry screens (see descriptions below).
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Profile Screen. The Profile screen (Figure 3) allows the recorder to
create a sketch of the sediment column with the pen stylus and save it. Editing
functions are also included to clear the entire sketch pad or undo the last pen
stroke. The profile sketches from each probe are saved as bitmaps and stored in
the Windows directory. File names can be created for these drawing files that
directly tag the survey unit or site so that subsequent integration with
associated probe data is readily facilitated. Each sedimentary unit or deposit
identified in the sketch is numbered in descending order and described in
detail by selecting the appropriate number from the Deposit Entry pick list in
the upper right corner of the screen. Maximum number of sedimentary units is
currently set at 30, although this figure can be augmented if necessary. By
clicking on the OK button after a deposit number has been selected, the Deposit
Entry screen appears.
 Figure 3
Probe Content Screen. The Probe Content screen is used to record artifact and/or feature categories recovered in a given probe using the Artifacts Present and Features Present pick lists. These pick lists can be customized for use within a given region or according to user preferences. For example, the Artifacts Present pick list could reflect only the most basic of artifact categories, or it could enumerate complex ceramic or lithic typologies. The screen permits the user to record these categories by depth if desired. In addition, the number of specimens recovered can also be associated with a given artifact category. For example, one piece of historic glass and three prehistoric potsherds recovered in the 0-20 cm level of a shovel probe can be recorded as "0-20cm - (h) glass - (3)" and "0-20cm - (p) sherd - (3)." An Archaic projectile point located at 47 cm below surface could be recorded as "47cm - (p) proj. pt., Ar - (1)." The customization capability of the Features Present pick list can also be put to use by soil geomorphologists and pedologists for recording geomorphological features by depth or depth range. This is especially useful for pedological features not accommodated on the Deposit Entry screen such as inclusions, clay films, concretions, pores, etc. Some examples would be: "50-85cm - (g) clay films; 175cm - (g) T.C. paleosol; 223-260cm - (g) CaCO3 blebs; 630-675cm - (g) rounded pebbles." Note that in all of these examples, a prefix is used to distinguish the general category of item being described;e.g., (p) = prehistoric, (g) = geological. There are length limitations on these entries, so coding should be standardized and as abbreviated as possible.
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Module 4: Querying and Generating Reports. The system has separate graphic user interfaces (GUI's), which support full SQL querying and report-generation capabilities within the FieldNotes software environment (Figure 4). These interfaces were also created with Microsoft's Visual Basictm programming language. The querying capability has been developed to accommodate "predefined querying" with the pen stylus, as well as standard querying with SQL (Structured Query Language) expressions with keyboard or pen input. In both cases the user can sort and group the probe data according to a number of different data fields, as well as integrate the bitmap drawings directly into the same output. In Predefined Querying, sorting and report generation can be carried out for administrative information, deposit information, artifact information, and/or feature information. However, the SQL expressions provide even greater flexibility in querying. Both of these querying modes are partially illustrated in the Query dialog box in Figure 4. A Query Report with hypothetical probe data is superimposed over it. The Query dialog box also provides a "quick reference" button for information on the database structure that can be consulted prior to querying. The queried tables can be displayed on the screen (as shown in Figure 4), printed to a printer, or saved in Microsoft EXCELtm format (.xls files) for further manipulation and data display in that spreadsheet program.
Conclusion
Systematic subsurface testing over an extensive landscape, whether it is
carried out for archaeological or strictly pedological purposes, is an
extremely expensive, labor-intensive endeavor. While there is little that can
be done to lower the high costs associated with the manpower and equipment
requirements of the probing itself, considerable savings can be realized in
field recording, data integration, and data analysis through the automation of
field data collection. ProbeCorder has been developed with these considerations
in mind. The cost-effectiveness of the system is achieved by elimination of
tedious and error-prone database entry and digitizing required by the use of
paper field forms and sketch maps. The ProbeCorder system provides substantial
benefits to archaeologists, geomorphologists, and pedologists by effectively
reducing the cost of subsurface surveys and by significantly enhancing data
integrity and information retrieval capabilities through fully automated field
recording. The system will be especially useful as a cost-effective data
capture tool for projects involving three-dimensional GIS representations of
stratigraphy for soil/landscape analysis [e.g., J. Raper, (ed.), 1989, Three
Dimensional Applications in Geographic Information Systems. Taylor and
Francis, London; S. J. Ventura, B. J. Irvin, B. K. Slater, and K. McSweeney,
1996, Data Structures for Representation of Soil Stratigraphy. In GIS and
Environmental Modeling: Progress and Research Issues. M. Goodchild, L.
Steyaert, B. Parks, C. Johnston, D. Maidment, M. Crane, and S. Glendinning,
(eds.) pp.63-68. GIS World Books, Ft. Collins, Colo.].
The ProbeCorder software (Version 1.0) is currently undergoing beta-testing for technology transfer within the Department of Defense. The program is contained on four 3.5" 1.44MB HD diskettes and is ready for installation in PenMetric's FieldNotes or as a stand-alone system loaded directly into the Windows-for-Pentm operating system. It can also be installed in a desktop PC running the Windows 3.1tm operating system, in which case the mouse can be utilized as a pen substitute. It has also been successfully installed on the Windows 95tm operating system, but full testing has not been undertaken since so few pen computers are capable of running Windows 95. Complete user documentation is also available (J. A. Zeidler, Y. Dong, and W. Song, 1997, User's Manual for ProbeCorder (Version 1.0) Data Collection Software. U.S. Army Construction Engineering Research Laboratories (USACERL), ADP Report 97/24. To be published and distributed by the U. S. Army Environmental Center, Aberdeen Proving Ground, Md.). Potential commercialization of the ProbeCorder module is currently being explored through a cooperative research agreement with major developers of pen-based software. For additional technical information on the ProbeCorder data collection software, the author may be contacted by email at j-zeidler@cecer.army.mil.
Note: Any discussion of specific products or any views or opinions expressed herein are solely those of the author and do not represent either the views or policies of any agency of the federal government, including the U. S. Army or the U. S. Army Corps of Engineers, Construction Engineering Research Laboratories.
James A. Zeidler is a principal investigator in the Tri-Services Cultural Resources Research Center of the U. S. Army Construction Engineering Research Laboratories (Champaign, Ill.) and a research associate of the Department of Anthropology, University of Illinois at Urbana-Champaign.