14°

110° W

17°

16°

15°

13°

13°

14°

15°

16°

17°

109° W 108° W 107° W

106° W

105° W

110° W 109° W 108° W 107° W 106° W

105° W

MC–17

MC–2

MC–3

MC–4

MC–8 MC–9 MC–10 MC–11

MC–1

MC–16 MC–18 MC–19

MC–24

MC–25

MC–26

MC–30

120°

120° 60°

60°

0°

30°

65°

180° 135° 90° 45° 0°

–30°

–65°

0°

30°

65°

–30°

–65°

14°

17.5°

250° E

17°

16°

15°

13°

12.5°

12.5°

13°

14°

15°

16°

17°

17.5°

251° E 252° E 253° E

254° E

255° E

250° E 251° E 252° E 253° E 254° E

255° E

2000

4000

6000

7000

9000

10,000

12,000

14,000

16,000

2000

2000

Ascraeus Sulci

ASCRAEUS

MONS

NOTES ON BASE

This map, compiled photogrammetrically from Viking Orbiter stereo image pairs, is part 

of a series of topographic maps of areas of special scientific interest on Mars.

MTM 500k 15/252E OMKT: Abbreviation for Mars Transverse Mercator; 1:500,000 series; center of sheet latitude 15° N., longitude 252.5° E. in planetocentric coordinate system (this corresponds to 15/107; latitude 15° N., longitude 107.5° W. in 

planetographic coordinate system); orthophotomosaic (OM) with color-coded 

(K) topographic contours and nomenclature (T) [Greeley and Batson, 1990]

ADOPTED FIGURE

The figure of Mars used for the computation of the map projection is an oblate spheroid 

(flattening of 1/176.875) with an equatorial radius of 3396.0 km and a polar radius of 

3376.8 km (Kirk and others, 2000). The datum (the 0–km contour line) for elevations is 

defined as the equipotential surface (gravitational plus rotational) whose average value at 

the equator is equal to the mean radius as determined by Mars Orbiter Laser Altimeter 

(MOLA; Smith and others, 2001).

PROJECTION

The projection is part of a Mars Transverse Mercator (MTM) system with 20° wide 

zones. For the area covered by this map sheet the central meridian is at 250° E. (110° W.). 

The scale factor at the central meridian of the zone containing this quadrangle is 0.9960 

relative to a nominal scale of 1:500,000.

COORDINATE SYSTEM

Longitude increases to the east and latitude is planetocentric as allowed by IAU/IAG 

standards (Seidelmann and others, 2002) and in accordance with current NASA and 

USGS standards (Duxbury and others, 2002). A secondary grid (printed in red) has been 

added to the map as a reference to the west longitude/planetographic latitude system that 

is also allowed by IAU/IAG standards (Seidelmann and others, 2002) and has been used 

for previous Mars maps.

CONTROL

Horizontal and vertical control was established using the Mosaicked Digital Image Model 

2.0 (MDIM 2.0; Kirk and others, 2000) and MOLA data. A portion of MDIM 2.0 covering the mapping area was extracted in simple cylindrical projection. This MDIM image 

was georeferenced to the MOLA data with an affine transformation. The MDIM image 

and georeferencing information were imported into a digital photogrammetric workstation (Miller and Walker, 1993) and used as an orthophoto to provide horizontal control to 

stereopairs of Viking imagery. The horizontal information was used to extract vertical 

control from the MOLA data. Note that the distribution of Viking Orbiter images suitable 

for mapping at a scale of 1:500,000 is uneven. Areas mapped in this series are chosen, 

often in blocks of two or more adjacent quadrangles, based on scientific interest as well 

as on the availability of suitable data for accurate mapping.

CONTOURS

Contours were derived from a digital terrain model (DTM) compiled on a digital photogrammetric workstation using Viking Orbiter stereo image pairs with orientation parameters derived from an analytic aerotriangulation. Contours were drawn automatically using 

a commercial geographic information system (GIS) software package (Environmental 

Systems Research Institute, 1994). For the stereomodels, the local expected vertical precision, based on image resolutions, parallax-to-height ratio (that is, convergence angle), 

and a matching accuracy of 0.2 pixel ranges from 43 m to 80 m, with a mean of 75 m. Elevation (in meters) is given with respect to the adopted Mars topographic datum (see 

"Adopted Figure" section). A comparison of the DTM values at the MOLA point locations shows that the DTM is on average 0.4 m lower than the MOLA points (n=245,058; 

μ=-0.4 m; σ=12 m). Contour lines were generated automatically using GIS software and 

were not edited. Because the contour lines were not edited, small closed contour lines, 

contour lines that intersect, and contour lines that do not match features are present. The 

post spacing for the DTM is 600 m; features that are less than 600 m in size will not be 

resolved and features that are smaller than 1800 m in size may only have four elevation 

measurements associated with them. This lack of elevation measurements may result in 

contour lines that do not adequately represent some features. The purpose of this mapping 

project is to produce the digital orthophoto and DTM. This map provides a graphical representation of the digital products that are available.

IMAGE BASE

The image base for this map employs Viking Orbiter images from orbits 090, 055, 892, 

and 643. An orthophotomosaic was created on the digital photogrammetric workstation 

using the DTM compiled from stereo models. Integrated Software for Imagers and Spectrometers (ISIS; Torson and Becker, 1997) provided the software to project the orthophotomosaic into the Transverse Mercator Projection.

REFERENCES

Duxbury, T.C., Kirk, R.L., Archinal, B.A., and Neumann, G.A., 2002, Mars Geodesy/Cartography Working Group Recommendations on Mars Cartographic Constants 

and Coordinate Systems, in Joint International Symposium on Geospatial Theory, 

Processing and Applications, Ottawa, Canada, 2002, Commission IV, Working Group 

9—Extraterrestrial Mapping, Proceedings: Ottawa, Canada, International Society for 

Photogrammetry and Remote Sensing [http://www.isprs.org/commission4/proceedings/paper.html].

Environmental Systems Research Institute, 1994, Arc commands: Redlands, Calif., Environmental Systems Research Institute, Inc.

Greeley, Ronald, and Batson, R.M., 1990, Planetary mapping: New York, Cambridge 

University Press, p. 261–276.

Kirk, R.L., Lee, E.M., Sucharski, R.M., Richie, J., Grecu, A., and Castro, S.K., 2000, 

MDIM 2.0—A revised global digital image mosaic of Mars, in Lunar and Planetary 

Science XXXI: Houston, Lunar and Planetary Institute, abstract 2011 [CD–ROM].

Miller, S.B., and Walker, A.S., 1993, Further developments of Leica Digital Photogrammetric Systems by Helava, ACSM/ASPRS Annual Convention and Exposition, 

Technical Papers, v. 3, p. 256–263.

Seidelmann, P.K. (chair), Abalakin, V.K., Bursa, M., Davies, M.E., De Bergh, C., Lieske, 

J.H., Oberst, J., Simon, J.L., Standish, E.M., Stooke, P., and Thomas, P.C., 2002, 

Report of the IAU/IAG Working Group on Cartographic Coordinates and Rotational 

Elements of the Planets and Satellites: 2000: Celestial Mechanics and Dynamical 

Astronomy, v. 82, p. 83–110.

Smith, D.E., Zuber, M.T., Frey, H.V., Garvin, J.B., Head, J.W., Muhleman, D.O., Pettengill, G.H., Phillips, R.J., Solomon, S.C., Zwally, H.J., Banerdt, W.B., Duxbury, T.C., 

Golombek, M.P., Lemoine, F.G., Neumann, G.A., Rowlands, D.D., Aharonson, O., 

Ford, P.G., Ivanov, A.B., McGovern, P.J., Abshire, J.B., Afzal, R.S., and Sun, X., 

2001, Mars Orbiter Laser Altimeter (MOLA)—Experiment summary after the first 

year of global mapping of Mars: Journal of Geophysical Research, v. 106, p. 

23,689–23,722.

Torson, J.M., and Becker, K.J., 1997, ISIS—A software architecture for processing planetary images (abs.), in Lunar and Planetary Science Conference XXVIII: Houston, 

Lunar and Planetary Institute, p. 1443.

NORTH

WEST

SOUTH

EAST

The following is a list of image pairs used to produce the 

topographic information for this map. Numbers below correspond to the numbers on the diagram above. Shaded area 

indicates MOLA data.

 ID IMAGE PAIR

 1 090A52/055A27

 2 892A07/643A49

 3 892A08/643A76

 4 892A09/643A76

 5 892A09/643A78

 6 892A10/643A75

 7 892A10/643A76

 8 892A11/643A75

 9 892A12/643A75

MTM 15/252E QUADRANGLE VIKING STEREOMODEL COVERAGE

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Dimensional calibration may vary between electronic plotters and between X and Y 

directions on the same plotter, and paper may change size due to atmospheric conditions; therefore, scale and proportions may not be true on plots of this map.

Digital files available on World Wide Web at http://geopubs.wr.usgs.gov/i-map/i2795

Topographic Map of the Northwest Ascraeus Mons Region of Mars

MTM 500k 15/252E OMKT

By

U.S. Geological Survey

2004

QUADRANGLE LOCATION

Photomosaic showing location of map area. An outline of 

1:5,000,000-scale quadrangles is provided for reference.

3

7

5 2 8

4

9

6

1

Prepared on behalf of the Planetary Geology and Geophysics Program, Solar System Exploration Division, Office of Space Science, 

National Aeronautics and Space Administration.

Manuscript approved for publication June 23, 2003

10 20 30 40 50 60 80 90 70 100 

SCALE 1:502 000 (1 mm = 502 m) AT 250° E (110° W) LONGITUDE

TRANSVERSE MERCATOR PROJECTION

KILOMETERS

CONTOUR INTERVAL 250 METERS

DASHED LINES REPRESENT 125-METER CONTOUR LINES

Planetocentric latitude and east longitude coordinate system shown in black.

Planetographic latitude and west longitude coordinate system shown in red.

10

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

GEOLOGIC INVESTIGATIONS SERIES I–2795

Version 1.0

Prepared for the

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

18,000 

17,750 

17,500 

17,250 

17,000 

16,750 

16,500 

16,250 

16,000 

15,750 

15,500 

15,250 

15,000 

14,750 

14,500 

14,250 

14,000 

13,750 

13,500 

13,250 

13,000 

12,750 

12,500 

12,250 

12,000 

11,750 

11,500 

11,250 

11,000 

10,750 

10,500 

10,250 

10,000 

9750

9500 

9250 

9000 

8750 

8500 

8250 

8000 

7750 

7500 

7250 

7000 

6750 

6500 

6250 

6000 

5750 

5500 

5250 

5000 

4750 

4500 

4250 

4000 

3750 

3500 

3250 

3000 

2750 

2500 

2250 

2000 

1750 

1500 

1250

Contour Guide, in meters