Field Automation UsingPen Computing andLaser Range Finder

Technologies

United StatesDepartment ofAgriculture

Forest Service

Technology &DevelopmentProgram

2300—Recreation ManagementSeptember 19989823 1209—SDTDC

Information contained in this document has been developed for the guidanceof employees of the Forest Service, USDA, its contractors, and cooperatingFederal and State agencies. The Department of Agriculture assumes noresponsibility for the interpretation or use of this information by other than itsown employees. The use of trade, firm, or corporation names is for the informationand convenience of the reader. Such use does not constitute an officialevaluation, conclusion, recommendation, endorsement, or approval of anyproduct or service to the exclusion of others that may be suitable.

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To file a complaint, write the Secretary of Agriculture, U.S. Department ofAgriculture, Washington, DC 20250, or call 1-800-245-630 (voice) or 202-720-1127 (TDD). USDA is an equal opportunity employer.

Field AutomationUsing Pen Computingand Laser RangeFinder Technologies

Frank SuttonCivil Engineer

USDA Forest ServiceSan Dimas Technology and Development CenterSan Dimas, California

September 1998

CONTENTS

INTRODUCTION................................................................................................................................ 1LASER SURVEY SYSTEM PROJECT .............................................................................................. 1EXISTING FIELD SURVEY PROBLEMS .......................................................................................... 1COMPONENTS OF A REAL TIME MAPPING SYSTEM ................................................................... 1 GPS Receivers .............................................................................................................................. 1 Laser Range Finders..................................................................................................................... 2 Laser Instrument Limitations ......................................................................................................... 2MAPPING SOFTWARE ..................................................................................................................... 3 Penmap, A Real-Time Mapping Application .................................................................................. 4 Archsite ......................................................................................................................................... 6PEN-BASED COMPUTERS .............................................................................................................. 7RECOMMENDATIONS ...................................................................................................................... 7LITERATURE CITED ......................................................................................................................... 8APPENDIX ......................................................................................................................................A-1REAL-TIME MAPPING AND DATA COLLECTION SOFTWARE ...................................................A-3PEN-BASED AND OTHER RUGEDIZED COMPUTER MANUFACTURERS ................................A-3LASER RANGE FINDER MANUFACTURERS ...............................................................................A-3

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INTRODUCTION

Recent advances in rugged field computers andpowerful pen-based mapping software haveprompted a reevaluation of the current methodsused by the USDA Forest Service to capturegeographic information system (GIS) data. The SanDimas Technology and Development Center(SDTDC) is exploring alternative feature positioningsystems such as laser range finders. Combiningthis technology with a pen-based data managementplatform and global positioning systems (GPS) willpotentially increase field data collection speed,quality, and efficiency. The “real-time” mappingapproach provided with current pen-based mappingsoftware will minimize site revisits by providing thesurveyor instant error checking while at the site,decreasing the likelihood of missing or incorrectdata. Pen-based mapping software will interfacewith an array of data measurement or input devices,such as total stations, GPS receivers, laser rangefinders, and digital cameras.

This report will introduce pen-based mappingsystems and focus on the laser range finder as ameans of rapidly obtaining feature positions for amultitude of USDA Forest Service mappingapplications. Penmap, by Condor EarthTechnologies, and Archsite, a Penmap applicationfor archeological sites, will be examined in detail.

As a reference, the appendix contains informationon hardware and software vendors. Note: Thisreport assumes the reader is familiar with basicsurvey and computer terminology.

LASER SURVEY SYSTEM PROJECT

Initially, this project was confined to data capturefor archeological sites. However, it soon becameapparent that the same mapping systems could alsobe applied to other Forest Service data collectionneeds, such as roads, trails, recreation sites,facilities, and streams.

In early 1996, a questionnaire was sent out to USDAForest Service recreation, archeological, andengineering staff to solicit information on surveyroutines and data usage requirements. Thequestionnaire results may be viewed from the USDAForest Service Web site listed below.

EXISTING FIELD SURVEY PROBLEMS

The main cause of errors in the field is the inabilityto immediately observe end results of data collection.Real-time mapping provides instant feedback sodata can be seen as it is collected. Reduction ofany raw measurements occurs immediately, andwhat is displayed on the field computer’s screen isthe map as it is being built. Traditionally,visualization of data occurs after post-processingthe data on the office computer. Up to this point,the surveyor may not be aware of errors or omissionsin the data. Errors that may occur with theconventional post-processing approach are:

• Missing features that are not detected while inthe field

• Not enough data are gathered; site is only partiallysurveyed

• Errors caused by an equipment malfunction• Inconsistency between electronically stored data

and any field sketches that are drawn, ormisinterpretation of sketches.

Validation of data is an important aspect of anysurvey. Errors may result from surveyors eitherpartially or completely forgetting to survey certainfeatures. These features are difficult to catch if thereis nothing to relate back to. When a check plot isobserved in the office, errors are not alwaysapparent. Part of the motivation of a real-timemapping approach is that these errors will becomeobvious and can be corrected while the surveyor isstill in the field.

COMPONENTS OF A REAL-TIME MAPPINGSYSTEM

A system containing the following components issuggested. Each of these components will bediscussed in detail.

• GPS receivers• Laser range finders• Core mapping applications• Pen-based computers.

GPS Receivers

Inexpensive and compact P(Y) coded GPS receiversare now available for use by the USDA ForestService. These units will remove the effects of

http://fsweb.sdtdc.wo.fs.fed.us/programs/rec/laser_survey/questionnaire.html

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selective availability imposed by the Department ofDefense. The latest receivers have been shown tobe effective under forest canopy conditions, and nowmay produce real-time accuracies adequate for themajority of USDA Forest Service resource mappingneeds. Publications on these and other receiversare available from the Missoula Technology andDevelopment Center:

Phone: (406) 329-3978;IBM mail: pubs/wo,mtdc;FSWeb: http://fsweb.mtdc.wo.fs.fed.us.

Laser Range Finders

Obtaining positional data with a reasonable level ofaccuracy using GPS devices has traditionally takentoo long, or has been hindered by dense canopy ordeep canyons that are common in many forestenvironments. Although there have been dramaticimprovements in GPS under these conditions, laserrange finders, sometimes called laser instrumentsor laser guns, offer an alternative by rapidly obtainingmeasurements of features without physicallyoccupying them.

Laser range finders are also useful for mappingsigns, utility poles, trees, topography, or otherfeatures. Features are mapped in a matter ofseconds by simply aiming and triggering theinstrument from a known point. Raw measurementsfrom the instrument’s sensors (distance, inclination,and azimuth) may be reduced to three-dimensionalcoordinates by a computer connected to theinstrument via an RS-232 interface.

Laser mapping instruments have different featuresand capabilities, and as such, will influence factorssuch as accuracy, minimum and maximum range,durability, and utility. They are typically hand-helddevices, with an aiming scope, that record distanceby measuring the time it takes laser light to travel toa target and reflect to a receiving diode in theinstrument. A series of measurements is taken andstatistically averaged to obtain the reading. Higher-priced models may include additional sensors that

measure tilt (inclination) and an electronic compassfor measuring azimuth, the angle referenced frommagnetic north. This gives laser instrumentsqualities similar to total stations, and givesthem theability to provide the three-dimensional coordinatesof a feature based on a known point.

SDTDC acquired a Criterion 400 from LaserTechnology, Inc. (LTI), in 1992 for the Low-VolumeRoads Survey Laser Project. The Criterion wasoriginally offered by LTI for forestry applications. Newrange finders manufactured by several differentcompanies have emerged since the debut of theCriterion. Laser Atlanta Optics, Inc., has released amodel competitive to the LTI Criterion, but at a muchlower cost. An evaluation of the various range-finderinstruments has taken place under a project fundedby the Forest Management program at SDTDC. Forresults, see Publication 9824 1307-SDTDCJune␣ 1998.

Laser Instrument Limitations

Experience with laser instruments in timber andengineering applications has shown that localattraction adversely affecting the azimuth readingsis a common problem under certain conditions.Large metal objects or subterranean ferromagneticdeposits, or anything capable of generating amagnetic field, will pull the azimuth reading well outof an acceptable range of accuracy. It is, however,possible to obtain X and Y coordinates byresectioning, calculating an unknown point bymeasuring distance to two or more known points(Figures 1 and 2). This is the technique used byGPS receivers for obtaining three-dimensionalposition information from distances measured fromsatellites. To derive a two-dimensional location fromtwo known points, an algorithm would need onlyazimuth to reduce a computation with two solutionsto one.

To test the feasibility of resectioning with a laserinstrument, a closed-loop test course was placed onthe grounds of SDTDC. Using a Criterion 400, atraverse was run using the instrument’s compass,

Figure 1—Resectioning with a Laser Range Finder.

distanceknown point

distance

laser instrumentoccupying unknownpoint

known point

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MAPPING SOFTWARE

Mapping/data-management software is availablefrom several vendors. Some of the featurescontained in off-the-shelf software packages areoutlined below:

1. Three-dimensional mapping capability. Theapplication must be able to store all coordinatesproduced by survey input devices, includingelevation.

2. A graphical user interface (GUI). Most pen-based applications run under a multi-taskingenvironment such as the Microsoft Windowsoperating system (OS), allowing the software torun on both field and office computers. Addingcapabilities to the mapping application would besimplified under the Windows OS by itsinterapplication communications capabilities,allowing other applications and drivers to senddata to the core mapping application. A largesoftware base of existing applications exists forWindows, extending the usefulness of the fieldcomputer. Examples of such software that canbe applied to field computing are handwriting andvoice-recognition engines. Another advantage ofa GUI is user-friendliness, minimizing the amountof training required for a user to become proficientwith the application. Instant on-line help isavailable, eliminating the need to carry softwaremanuals to the field.

averaging both foresight and backsightmeasurements of azimuth, vertical inclination, andslope distance. Reflector targets were used, withthe foliage filter placed on the instrument. Theinstrument and the targets were mounted on staffsthat were manually plumbed using a bubble level. Aprecision of 1 in 268 was calculated. Severalcompass readings were found to be outside therange of accuracy quoted by the manufacturer.

Additional points were placed both inside and outsidethe test traverse, so that a series of triangles formedaround the traverse. The traverse point coordinateswere calculated using the law of cosines, which relieson horizontal distances calculated on all legs of thetriangles. Azimuth was dropped and only slopedistance and vertical inclination were measured.Only one measurement was taken between allpoints. Precision with respect to the perimeter ofthe original traverse was calculated at 1 in 1,204,nearly a 4.5-fold increase.

A disadvantage of using this traversing technique isthe increased time required to take additionalmeasurements to known points. Since speed ofcollection is the main advantage of using a laserinstrument, it can be concluded that using one ismuch less advantageous if unknown features mustbe occupied. However, in situations where denseforest canopy disallow the use of GPS, the techniquemay be beneficial.

Figure 2—An example of establishing points for a site survey using a three-point resectioningtechnique that builds a survey from points located along a baseline.

base

line

base

line

base

line

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Figure 3—Various input devices of a field data-collection/mapping system.

3. Visual map display. A display of the map anddata being constructed in real time is what setsmodern mapping/data collection software apartfrom the software residing on traditional datarecorders. Rapid CAD-like panning and zoomingcapabilities ease the visualization of the data andspeed the collection process. All raw data andmeasurements are reduced before surveyedfeatures are plotted onto the display, making itunnecessary to post-process any data at theoffice.

4. GIS Capabilities. To provide a useful data-capture system that will interface well with theUSDA Forest Service GIS, modern mapping/data-collection software has the ability to recordmultiple-feature attributes that are tied to thespacial data. The ability to transfer selectedARC/INFO coverages from the USDA ForestService IBM system to the field computer, usefulfor field data validation, will be evaluated.

5. Database form customization. The ability todesign custom database forms that match differingUSDA Forest Service data requirementsincreases the versatility of the data-collectionsystem, making it useful for multiple resourceareas. GUI features, such as pull down lists andvoice actuated text boxes contained in thedatabase forms, speed attribute collection.

6. Interfaces to multiple input devices. With thelarge array of survey instrumentation such as GPSreceivers, laser range finders, total stations, andalternative input devices such as digital camerasand bar-code readers, flexible systems thatinterface with these devices are available(Figure␣ 3).

Penmap, A Real-Time Mapping Application

As this project was beginning, Region␣ 8 published areport, accompanied by a letter dated August 1, 1995addressed to Forest Supervisors, on using pencomputers for data collection. The letter stated thatsubstantial productivity gains were recognized byusing this new technology. Region␣ 8 recommendedPenmap as the core application for use with amapping system. After a SDTDC market search,several other programs were found, but noneseemed to offer the advanced survey methods or toincorporate as many input devices as Penmap. Asthe market continues to change, with more vendorsoffering improved mapping and data-collectionsystems, future evaluations will be needed to ensurethat USDA Forest Service field units are aware ofthe most applicable, cost-effective, and time-savingsolutions.

The Penmap application is an off-the-shelf productsold by Condor Earth Technologies of Sonora,California. It operates on IBM compatible computersrunning Microsoft Windows 3.1x or Windows␣ ‘95. Itcan be thought of as an electronic plane table,capable of recording survey measurements using avariety of input devices and survey methods.Penmap allows viewing and editing of data in realtime, eliminating the need for post-processing.Penmap is most useful running on a powerful pen-based computer with a 486 processor or higher.Some of Penmap’s more useful features are outlinedbelow:

1. Multiple input methods. The Penmap applicationcollects spacial information from an array of surveyinstruments (see appendix) or by hand input.Survey methods such as traversing, chain andoffset, resectioning, and distance/bearing are

Pen Based Computer

Laser Instrument

Core Application

Digital Camera GPS

Import FilesRaster Images, ARC/INFO,

Autocad DXF, etc.

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provided with the software. Adjustment is possiblewith the traverse method. With the resectionmethod, up to six reference points may be usedin calculating the instrument’s location.Computation can be determined from angle anddistance, angle only, or distance only, the latterbeing useful for accurate positioning using laserrange finders.

2. Display of collected data over raster or vectormaps or images. Data can be displayed overdigital ortho quads or other images usingRasterback, a utility for importing raster imagesinto Penmap as a backdrop to a survey (Figure␣ 4).

3. User Customization. A form generator isprovided with Penmap to allow custom databaseforms to be constructed. Forms can be made tomatch a wide variety of data-collectionapplications (Figure␣ 5). The database formsrecord attributes and link them to a feature on theground. The form can be called and editedanytime during the survey. Database forms alsoaccept input from devices such as digital camerasand bar code readers. Users can also createcustom buttons that act as a shortcut to selectinga layer, survey method, graphic, or database formcorresponding to the feature being mapped.

4. On-site dynamic terrain modeling (DTM).Penmap includes powerful three-dimensionalterrain modeling features previously found onlyon high-end office CAD systems, but with theadded advantage of instant data visualization andon-site error checking (Figure␣ 6). The softwareallows the dynamic generation of contours asthree-dimensional points are gathered. Breaklines or barrier lines can be either constructeddynamically or by connecting existing points witha line. These DTM features can be useful toengineers or surveyors wishing to accuratelyconstruct surface models and compute volumeson site. Up to five surfaces can be generatedand their corresponding volumes computedrelative to a datum surface. A sectioning featurecomputes the line resulting from the intersectionof a vertical plane with an existing surface. Theprofile of the line is then displayed.

5. Multiple file import and export formats.Arc/Info, Autocad DXF, Genio, and others aresupported.

Penmap software with standard instrument interfaceis available to the USDA Forest Service for $995.Penmap with GPS interface costs $1,895. The licenseagreement allows one installation of Penmap on afield computer and one installation on an office PC.

Figure 4—A raster image derived from a USGS 7.5’ quadrangle is displayed in the Archsite application using Rasterback, a feature ofPenmap for Windows (courtesy of Condor Earth Technologies).

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Figure 6—Fujitsu Stylistic 1200 Pen Computer (Courtesy of Pen Computing Magazine).

Figure 5—A database form in Penmap constructed for stream inventories (courtesy of Condor Earth Technologies).

Archsite

Archsite, a partnership between Condor EarthTechnologies and the USDA Forest Service SouthernRegion, is a customization of Penmap to capturearcheological data and export it to the appropriateState Historical Preservation Office form. A reporton Archsite and its configuration files is available,and further information can be obtained from KentSchneider, Heritage Program Manager, SouthernRegion.

Archsite configuration files for Penmap are publicdomain and can be obtained from the USDA NationalForest Region 8 office or Condor Earth Technologies,Inc. More information can be obtained from CondorEarth Technologies, Inc., 21663 Brian Lane, Sonora,CA 95370. Phone: (209) 532-0361. Internet:http://www.condorearth.com.

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PEN-BASED COMPUTERS

Computer hardware has gone through remarkablechanges in recent years. Smaller size, increasedprocessor power, increased storage capacity anddecreased cost have been some of the technologicalchanges that have taken place. Computer historytells us that the trends will continue, with moremanufacturers producing low cost, ruggedizedcomputers capable of meeting the demands of USDAForest Service field personnel. Recently, new modelsof pen-based computers are appearing that offerfeatures that make mobile computing in harsh fieldconditions possible, while maintaining thefunctionality of desktop computers. Fieldruggedness, compactness, low power consumptionand user-friendliness have become the focus ofmany of the manufacturers.

A pen computer (or pen-based computer) consistsof a flat display with an incorporated digitizer thatrecords the traces of a pen (stylus) in contact withthe display surface. The pen is the input device thatreplaces the traditional mouse and keyboard foundon desktop computer systems (Figure 7).

The majority of the pen computers on the marketuse a monochrome liquid crystal display (LCD) andan Intel 80486DX compatible processor. Processorsmanufactured by Advanced Micro Devices havebecome a popular choice by makers of pencomputers because of low heat output anddecreased power requirements, but theseprocessors do not offer near the CPU speed asnewer desktops computers. Several of the latestmodels of pen computers offer Intel Pentium CPUs.Batteries are generally nickel metal hydride or lithiumion, and typically last a maximum of four hours, so itis essential that a sufficient number of batteries betaken along for field work.

Sufficient computing power is essential whenselecting a pen computer. Tasks such as handwritingrecognition are CPU intensive and requireimmediate feedback to the user. Having adequaterandom access memory will speed graphical orientedapplications.

Pen computers range in price from $2,000␣ to␣ $7,000,depending on configuration and performance. Seethe appendix for pen computer vendor contactinformation.

RECOMMENDATIONS

Because the market for field data-collection-systemcomponents is changing very rapidly, and furtherinvestigation and evaluation are required, the projectwill continue. Further work in customizing a field data-collection system to meet differing resource needswill be developed. Additional information regardingthis project may be found at the website listed below.

Figure 7—Operator with pen-based computer receiving inputfrom a Laser Technology, Inc., Criterion 400 laser survey

instrument. Computer is a ALPS, Inc. Kalidor 2500 pen-basedcomputer (no longer manufactured).

http://fsweb.sdtdc.wo.fs.fed.us/programs/eng/gis/gis.html

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LITERATURE CITED

Bernard, J., “Attribute Collection and GPS.” Proceedings from 1994 AM/FM International Conference.

Bradshaw, M. and B. Zykan. “Increasing Productivity using Laser Mapping Systems.” Proceedings from 1994AM/FM International Conference.

Elliott, B. “Moving AM/FM to the Field: Technology, Trends and Success Stories.” Proceedings from 1994 AM/FM International Conference.

Griswold, G. “Field Application and Review of Hand-Held Laser Instrument Grand Mesa, Uncompahgre, andGunnison National Forests, Gunnison Engineering Zone.” USDA Forest Service Engineering Field Notes,May-August 1994.

Kent W. K. Lam, and Albert W. K. Chow. “A Topologically Integrated Field Data Capture System.” Proceedingsfrom 1994 Urban and Regional Information Association.

Lee A. Graham. “Land, Sea, Air GPS/GIS Field Mapping Solutions for Terrestrial, Aquatic and Aerial Settings.”GIS World, January 1997.

Moll, J. “Low-Volume Roads Survey Laser.” Project Report, San Dimas Technology and Development Center,June 1993.

Moll, J., M. Harrison, R. Turner, and W.F. Sutton. “The Spelunker’s Delight: Cave Surveying Made Easy.” ProjectReport, San Dimas Technology and Development Center, February 1995.

Nunnelley, G., G. Wood, and K. Schneider. “Archsite: Innovative Software for Heritage Field Data Collectionand More.” Proceedings from 1997 ACSM/ASPRS Convention and Exposition.

APPENDIX

APPENDIX

REAL-TIME MAPPING AND DATA COLLECTION SOFTWARE

Penmap GeoLink VoCartaCondor Earth Technologies GeoResearch, Inc. Datria Systems Inc.(209)-532-0361 (800)-436-5465 (800)-583-9509http://www.condorearth.com http://www.georesearch.com http://www.datria.com

Field Notes Aspen Conic GISPenmetrics Inc. Trimble Navigation Ltd. Conic Systems, Inc.(541)-752-9000 http://www.trimble.com (210)-832-0100http://www.penmetrics.com http://www.conic.com

FieldSmartMapFrame Corporation(214)-741-2264http://www.mapframe.com

PEN-BASED AND OTHER RUGEDIZED COMPUTER MANUFACTURERS

Walkabout Computers Fujitsu Telepad(561)-881-9050 (800)-831-3183 (703)-834-9000http://www.walkaboutcomp.com http://www.fpsi.fujitsu.com http://www.telepad.com

Texas Micro Itronix Teklogix(800)-627-8700 (800)-441-1309 (800)-633-3040http://www.texmicro.com http://www.itronix.com http://www.teklogix.com

Norand Corp. Husky Computers Microslate(800)-553-5971 (813)-530-4141 (514)-444-3680http://www.norand.com/terminals.html http://www.wpihusky.com http://www.microslate.com

LASER RANGE FINDER MANUFACTURERS

Criterion, Impulse AdvantageLaser Technology Inc. Laser Atlanta, Inc.(303)-649-1000 (770) 446-3866http://www.lasertech.com http://www.laseratlanta.com

For up-to-date information listed in this appendix, visit the SDTDC FSWeb site at:

http://fsweb.sdtdc.wo.fs.fed.us/programs/eng/gis.html

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