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T o p o g r a p h i c

E n g i n e e r i n g C e n t e r

E R D C / T E C T

N - 0 0 - 1

Generating a Coastal Boundary andMerging Bathymetry with DTED® Level 1

Using ArcInfo: A Modeling and Simulation Application June 200

James J. Damron

Approved for public release; distribution is unlimited.





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iii

TABLE OF CONTENTS

PAGE

LIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

PREFACE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

COASTAL BOUNDARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

MERGING BATHYMETRY WITH DTED LEVEL 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

APPENDIX - XYX2GRID.AML . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

LIST OF FIGURES

FIGURE PAGE

1 DTED Level 1 with DCW Coastal Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 Gridded Lines and Generalized Coastal Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3 Generalized Coastline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 Zoomed-in View of Figure 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5 Splined Coastal Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

6 Zoomed-in View of Figure 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 7 Generalized versus Splined Comparison . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

8 DCW Coastal Lines and DTED Level 1 Generated Coastal Lines . . . . . . . . . . . 10 9 DCW Coastal Lines and DTED Level 1 Generated Coastal Lines . . . . . . . . . . . 11

10 DCW Coastal Lines and DTED Level 1 Generated Coastal Lines . . . . . . . . . . . 1211 DCW Coastal Lines and DTED Level 1 Generated Coastal Lines . . . . . . . . . . . 13

12 DCW Coastal Lines and DTED Level 1 Generated Coastal Lines . . . . . . . . . . . 1413 Flow Chart of the Coastal Generation Process . . . . . . . . . . . . . . . . . . . . . . . . . . 15

14 UTM.PRJ File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1615 DTED Level 1 Clipped to Coastal Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

16 Bathymetry Clipped to Coastal Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1917 Before the SELECTMASK Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

18 After the SELECTMASK Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

19 After the GRIDINSERT Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2220 After the CON Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2321 After the CON and ISNULL Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

22 Color-Shaded Relief of Bathymetry/Terrain Merge . . . . . . . . . . . . . . . . . . . . . . 2523 Flow Chart of the Merging Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27



iv

PREFACE

This project was completed during the period February to April 2000. Mr. Thomas E.

Jorgensen was Chief, Terrain Data Representation Branch, and Mr. William Z. Clark was Acting

Director, Topographic Research Division during this period.

Colonel James A. Walter was the Director of the U.S. Army Engineer Research and

Development Center’s (ERDC) Topographic Engineering Center (TEC) at the time of publication

of this report.

ACKNOWLEDGMENTS

Appreciation is hereby giver to the following ERDC/TEC employees who assisted in the

review of the applied methodologies used within the report: Jamie Richardson, OperationsDivision, Products and Services Branch, and Doug Caldwell, Terrain Research Division, Terrain

Data Generation Branch.



1

GENERATING A COASTAL BOUNDARY AND

MERGING BATHYMETRY WITH DTED® LEVEL 1

USING ARCINFO: A MODELING AND SIMULATION APPLICATION

INTRODUCTION

The Environmental Systems Research Institute’s (ESRI) Digital Chart of the World (DCW) arevector data created from the National Imagery and Mapping Agency’s (NIMA) (formerly the

Defense Mapping Agency’s (DMA)) Operational Navigation Chart (ONC) at 1:1,000,000 scale.Use of DCW poses a potential problem when working with other digital data at higher

resolutions. The PONET and POLINE vector layers in the DCW, which identify a coastal boundary, are not sufficient for modeling and simulation. The DCW coastal layers do not

register accurately with Digital Terrain Elevation Data (DTED®) Level 1. DTED Level 1 has anaccuracy equivalent to a 1:250,000-scale map product. DTED Level 1 is the main elevation

source used for modeling and simulation to create a terrain surface in a virtual world. The coastallayers in DCW are quite effective for most Geographic Information System (GIS) applications

but, for modeling and simulation purposes, the vector layers for a coastal boundary do notcorrelate with DTED Level 1 (Figure 1).

This report addresses two problems the modeling and simulation community has enduredwhen creating virtual databases. The first procedure will detail how to generate a coastal boundary vector from DTED Level 1 when other vector products are not adequate. In the second procedure, the new coastline will be used as a common boundary to merge bathymetry withDTED Level 1. ArcInfo version 8.0.1 with the GRID extension was the GIS software packageused for this project.

COASTAL BOUNDARY

The coastal boundary of any area is mainly dependant on tidal variations. This may present

problems when one decides to generate a coastal boundary from another source, such as DTEDLevel 1. The actual coastal boundary for mapping purposes is the average of the tidal variation

usually called mean sea level (MSL). There are no well-defined ocean-land boundary data inDTED Level 1, but generating a coastal boundary from these data will provide better correlation

between the ocean-land boundary, since the elevation data is in ellipsoid heights.

The coastal generation methodology will take several steps. This section will illustratehow to create a coastal boundary vectors that correlates with DTED Level 1. First, the SETNULL

function was used to eliminate the land terrain from the ocean surface at the GRID prompt. The

following string oceannull = setnull(mergeall > 0, mergeall) was used to set all data valuesabove 0 to NODATA. The ocean surface can be replaced by NODATA values in the sameSETNULL process, but either land or ocean are sufficient. Second, the GRIDPOLY command

was issued to generate a vector coverage with the command line gridpoly oceannull oceancov 1at the Arc prompt. Third, the GENERALIZE command was used to eliminate the boxy

appearance of the newly created oceancov vectors by using the string generalize oceancov



2

oceangen75 75 pointremove. In Figure 2, the vectors created in step 2 of the GRIDPOLY

conversion are colored white and appear boxy. The effects of the GENERALIZE command in

step 3 are apparent in Figure 2 by the elimination of the boxy appearance of the lines coloredmagenta.

In ArcEdit, a basic cleanup of the vectors is needed to create a usable vector coverage.Removal of dangling short lines, snapping lines together, and other procedures are needed beforecontinuing on to the next step. In Figure 3, the ArcEdit cleanup is completed with newly

generated coastlines correlating better to DTED Level 1 at this stage. A closer view in Figure 4shows the better correlation of the generated coastlines to DTED Level 1.

Fourth, all the lines were selected using the SELECT command with the all option at theArcEdit prompt with the string select all . Fifth, the GRAIN command is issued with a distanceset at 75 m with the following string grain 75. Sixth and final step, the SPLINE command wasused to provide curvature to the vector coverage and is more representative of the coastline. Theeffect of the SPLINE command is shown in Figure 5 with the new coastal lines shown in green.

In Figure 6, a closer view of the same area shows the splined coastal lines correlating better withDTED Level 1. A comparison of the generalized vectors and splined vectors are shown inFigure 7. Two large lake boundaries also were generated in the coastline generation method byselecting elevations at 230 m and 134 m above sea level.

The improved correlation of the coastal boundary vectors within DTED Level 1 areapparent in several figures. The magenta-colored and green-colored lines represent the DTEDLevel 1-generated lines. The white-colored lines represent the DCW coastlines. The improvedcorrelation is apparent in Figure 8 with the generated vectors lining up with DTED Level 1. TheDCW coastal lines are offset by as much as 1,000 m, or more, in most cases, compared to theDTED Level 1-generated lines. Also, the DCW coastal lines are very coarse and generalized

compared to the DTED Level 1-generated lines. In Figures 9, 10, and 11, the coastal and island boundaries are correlating better to DTED Level 1 data than the DCW coastal lines. It isapparent that smaller coastal island boundaries are captured and better correlated to DTED Level1 with coastline generation methods than the DCW coastal lines shown in Figure 12. Thisimprovement will help provide better correlation between coastal features and elevation data not before possible in modeling and simulation from other sources of data. A flow diagram in Figure13 provides the steps involved with generating a coastal boundary from DTED Level 1.



3

Figure 1. DTED Level 1 with DCW Coastal Lines



4

Figure 2. Gridded Lines and Generalized Coastal Lines



5

Figure 3. Generalized Coastline



6

Figure 4. Zoomed-in View of Figure 3



7

Figure 5. Splined Coastal Lines



8

Figure 6. Zoomed-in View of Figure 5



9

Figure 7. Generalized versus Splined Comparison



10

Figure 8. DCW Coastal Lines and DTED Level 1-Generated Coastal Lines



11




12




13




14




15

Figure 13. Flow Chart of the Coastal Generation Process



16

input projection geographicunits dddatum wgs84

parametersoutput projection utmunits meterszone 47datum wgs84

parametersend

Figure 14. UTM.PRJ File

MERGING BATHYMETRY WITH DTED LEVEL 1

The DTED Level 1-generated coastal boundary will provide a tool to clip bathymetry and DTEDLevel 1 to a common boundary for the merging process. The most common source of bathymetryis available on the U.S. Department of Commerce’s National Oceanic and Atmospheric

Administration’s (NOAA) National Data Center for Marine Geology and Geophysics at theTopography & Global Relief web site: www.ngdc.noaa.gov/mgg/bathymetry/relief.html. Click on the Global Relief & Elevation Models and click on the ETOPO5/TerrainBase to access the5-Minute Gridded Elevation Data Selection web site. This is the web site where the bathymetricand global 5-minute terrain data can be downloaded to the computer in different formats. Anyarea can be selected by using the following coordinates: Upper Left (UL) longitude, latitude, andLower Right (LR) longitude, latitude. The format chosen for this project was comma delimited,ASCII format, and Lon Lat Datavalue.

First, the downloaded data were converted from the ASCII format to a grid. This was

done by using the xyz2grid.aml file seen in the Appendix, which can be download from the

ESRI web site at www.esri.com under ArcInfo scripts. The AML was executed at the Arc prompt by typing the string &r xyz2grid indian.xyz oceandd . Second, the new grid had to be projected to a UTM projection, zone 47, and WGS 84 datum by using the PROJECTGRID

command at the Arc prompt. The following command line was issued projectgrid bathdd

bathutm utm.prj with a utm.prj file shown in Figure 14.



17

Third, the grid bathutm needed to have the same cell size as the DTED Level 1 data. The RESAMPLE function was issued with the following string bathres90 = resample(bathutm, 90,

bilinear) at the GRID prompt. Fourth, the bathres90 was clipped to the same area as DTEDLevel 1 by using a generated bounding box of the area. This was accomplished by using the LATTICECLIP command at the Arc prompt with the following command line latticeclip

bathres90 areaclip bathresclip minimum. Fifth, the bathymetry was ready to be clipped by theDTED Level 1-generated coastal vectors. Two different coverages were created in ArcEdit to produce the desired effect. The first coverage used the coastline with island boundaries to clip

the DTED Level 1 terrain shown in Figure 15. The second coverage used the entire ocean area toclip the bathymetry shown in Figure 16. The command LATTICECLIP from step 4 was used toclip the DTED Level 1 and bathymetry using the two different coverages. Sixth, the INT functionwas issued at the GRID prompt to convert the clipped bathymetry data to DTED Level 1 integer values using the string oceanint = int(oceanresclp).

Seventh, NODATA values for the islands are created and provide data to complete themerging process correctly. This was done by selecting the ocean and island polygons from the

DTED Level 1-generated coastal vectors. The ocean and island polygons were dumped into anew coverage by using the PUT command. An elev attribute field was added to the newocean/island polygons. The ocean polygon was given a value of 0 and the island polygons weregiven a value of -9999, which is a NODATA value. Eighth, the ocean and island polygons wereconverted to a grid by using the POLYGRID command with the string polygrid islandcov

islandmask elev at the Arc prompt. Ninth, the SELECTMASK function was used to mask out theislands from the clipped bathymetry. The following string was used to execute the processoceanmask = selectmask (oceanclp, islandmask) at the GRID prompt. The result of the maskingis shown in Figure 18 with the before-masking result shown in Figure 17.

Tenth, the GRIDINSERT command was used to merge the clipped DTED Level 1 and

masked bathymetry with the update option using the command line gridinsert oceanmask thailandclp landocean update at the Arc prompt. The result of the GRIDINSERT command isshown in Figure 19 with black areas near the coastline indicating NODATA values. The bathymetry elevations in the first bathymetry/terrain merge were found to be higher in certaincoastal locations, shown in Figure 19, by the bathymetry appearing higher than the land. Alisting of the bathymetry was made using the LIST command at the GRID prompt by using list

oceanmask.vat . The highest value found from the listing was 331 m. The CON function was used

to select values greater than -11 m to correct all the inlet waterways. The string oceancorr =

con(oceanmask > -11, -10, oceanmask) was used to perform this correction. The bathymetry and

terrain data sets were merged again using the GRIDINSERT command with the results shown inFigure 20. In the final step, the CON and ISNULL functions were issued at the GRID prompt to

eliminate the NODATA values on the coastline. The string landocnisnl = con(isnull(landocean),0, landocean) was used for the final process to make the NODATA values equal 0 with the

results seen in Figure 21. In Figure 22, the final delivered merged bathymetric/terrain data set isshown in a color-shaded relief.



18

Figure 15. DTED Level 1 Clipped to Coastal Lines



19

Figure 16. Bathymetry Clipped to the Coastal Lines



2 0

Figure 17. Before the SELECTMASK Function



2 1

Figure 18. After the SELECTMASK Function



22

Figure 19. After the GRIDINSERT Command



Figure 20. After the CON Function

2 3



2 4

Figure 21. After the CON and ISNULL Function



25

Figure 22. Color-Shaded Relief of Bathymetry/Terrain Merge



26

In the final step, it might not make sense to replace NODATA values with 0 values. Thisis just an approximation of the coastal boundary. The coastal boundary vectors in modeling and

simulation are used to help build a TIN and make the coastal ocean-land boundary equal to 0elevation. The elevation in the real world may be some other value. This approximation is

suitable for modeling and simulation because of the increase in correlation between the ocean-

land boundary not before possible in other construction efforts. The steps involved in themerging process are illustrated in Figure 23.

CONCLUSIONS

A coastal boundary line, which can be generated from DTED Level 1, will correlate better to theDTED Level 1 data than the DCW coastal boundary lines. The coastal boundary method allows

for the generation of vectors for a modeling and simulation database, which correlates well withDTED Level 1 data when no other sources are available. The generation of coastal vectors seems

to increase the number of features, such as islands. The coastal boundary vector also was used toclip DTED Level 1 and bathymetry to a common coastal boundary for the merging process.

The coastal boundary vectors and enhanced bathymetric/terrain data provide informationnot previously available to modeling and simulation for maneuvers by joint land, sea, and air operations using ArcInfo commands and functions. The coastal boundary method will guaranteea correlated result. The proposed methods can work with any elevation data set. Further investigation is needed to see if other data sets correlate better to DTED Level 1 and futureDTED products for modeling and simulation. Additional research is needed to study thecorrelation between higher resolution vector data sets and DTED products, as well as betweenhigher resolution elevation data sets.



27

Figure 23. Flow Chart of the Merging Process





29

APPENDIX - XYX2GRID.AML

/* xyx2grid.aml/*/* Creates a grid from a textfile containing X,Y,Z values.

/*/* History/* Stephen Lead, Original coding - 21 Jan, 2000/*/*&severity &error &routine bailout&args textfile grid

&call checkargs&call fileman

&call writefiles

&call generate&call finish

&return

/*&routine generate

/* Generate the point cover.

&s cover [scratchname -prefix xyz -directory]generate %cover%

input %tempfileXY%points

quitbuild %cover% points

/* Create an INFO file from the Z values.

&s zlist [scratchname -prefix xyz -info]tablesdefine %zlist%%cover%-id 4 5 belevation 10 10 n 4

~add from %tempfileZ%commitquit

/* Join the cover with the elevation values.



30

joinitem %cover%.pat %zlist% %cover%.pat %cover%-id %cover%-id

/* We get the cellsize by subtracting the distance between the first 2/*points in the textfile.

&s fileunit [open %textfile% openstat -read]&if %openstat% <> 0 &then

&do

&s str Error opening textfile %textfile%; &call bailout&end

&s X1 [extract 1 [read %fileunit% readstat]]&s X2 [extract 1 [read %fileunit% readstat]]&if %readstat% <> 0 &then

&do&s str Error reading textfile %textfile%; &call bailout&end

&s null [close %fileunit%]

&s gridsize [calc %x2% - %x1%]&if %gridsize% LE 0 &then

&do&s str Error setting output grid size; &call bailout&end

/* Finally, we do the point to grid conversion.pointgrid %cover% %grid% elevation%gridsize%

yesnodata

&return

/*&routine writefiles

/* Write the ID and XY to one file, the ID and Z to another. We need to

/* check that the values in the textfile are numeric.

&s ID = 0&s line [read %infileunit% readstat]

&do &while %readstat% = 0

&s ID = %ID% + 1&s x [extract 1 %line%]



31

&s y [extract 2 %line%]&s z [extract 3 %line%]

/* Check that values in the textfile are numeric.

&if [null %x%] | [null %y%] | [null %z%] | ~

[type %x%] > -1 | [type %y%] > -1 | [type %z%] > -1 &then&do&s str Bad value encountered in %textfile%: %line%

&call bailout&end

&s outlineXY [quote %ID% %x% %y%]&s outlineZ [quote %ID% %z%]&s writestatXY [write %XYfileunit% %outlineXY%]&s writestatZ [write %Zfileunit% %outlineZ%]&if %writestatXY% <> 0 | %writestatZ% <> 0 &then

&do&s str Error writing to temporary textfile;&call bailout&end

&s line [read %infileunit% readstat]&end

/* Append the word END to the XY file.&s writestatXY [write %XYfileunit% END]&if %writestatXY% <> 0 &then

&do&s str Error writing to temporary textfile;&call bailout

&end

&s null [close %XYfileunit%]&s null [close %ZFileunit%]

&return

/*&routine fileman

/* Open the textfile.

&s infileunit [open %textfile% openstat -read]&if %openstat% <> 0 &then

&do&s str Error opening textfile %textfile%; &call bailout

&end



32

/* Create a temporary textfile to hold the ID and X,Y values.&s tempfileXY [scratchname -prefix xyz -file]

&s XYfileunit [open %tempfileXY% openstat -write]&if %openstat% <> 0 &then

&do

&s str Error writing temporary textfile. Please check write permissions.&call bailout&end

/* Create a temporary textfile to hold the ID and Y values.&s tempfileZ [scratchname -prefix xyz -file]&s Zfileunit [open %tempfileZ% openstat -write]&if %openstat% <> 0 &then

&do&s str Error writing temporary textfile. Please check write permissions.&call bailout

&end

&return

/*&routine checkargs

&if [null %textfile%] | [quote %textfile%] = '#' &then &call usage&if [null %grid%] | [quote %grid%] = '#' &then &call usage&if [quote %textfile%] = 'usage' &then &call usage&if not [exist %textfile% -file] &then

&do&s str Can't find textfile %textfile%; &call bailout&end

&if [exist %grid% -grid] | [exist %grid% -cover] &then&do&s str Geodataset %grid% already exists; &call bailout&end

&return

/*

&routine finish

/* Delete the temporary files, covers, etc.&s null [delete %tempfileXY% -file]

&s null [delete %tempfileZ% -file]&s null [delete %zlist% -info]



kill %cover% all

&s str Grid %grid% with cellsize %gridsize% was generated from %textfile%...&call bailout

&return

/*

&routine usage

&s str Usage &r %aml$file% <xyz_textfile> <grid>&call bailout

/*&routine bailout

&severity &error &fail

/* Delete the temporary files and cover, if they've been created.&s null [close -all]&if [variable tempfileXY] &then &s null [delete %tempfileXY% -file]&if [variable tempfileZ] &then &s null [delete %tempfileZ% -file]&if [variable cover] &then

&if [exists %cover% -cover] &then kill %cover% all

&if not [variable str] &then &s str Bailing out of %aml$file%&return; &return &warning %str%

/*/* END OF FILE/*