LRO LOLA Gridded Data Record Shape Map (GDRDEM)
GDRDEM – Gridded Data Record Shape Map
Instrument: Lunar Orbiter Laser Altimeter
PDS Data Set ID: LRO-L-LOLA-4-GDR-V1.0DOI: 10.17189/1520642
PDS4 Bundle:urn:nasa:pds:lro_lola_rdrDOI: 10.17189/tnyt-7007
LRO PDS3 to PDS4 Migration Status: Complete
For more information about LOLA calibrated and derived products, see the RDR Product SIS.
For more information about the LOLA PDS3 volume, see the LOLA Archive Volume SIS.
The Lunar Orbiter Laser Altimeter (LOLA) Gridded Data Records (GDRDEM) data products are map-projected digital elevation models (shape models) derived from altimetry data acquired by the LOLA instrument. Each product uses data acquired through various mission phases. The GDRDEM data products contain the binned, interpolated altimetric measurements on a uniformly-spaced grid.
A pixel in the GDRDEM product represents the mean value at the center of a region bounded by lines of constant longitude and latitude at integral numbers of degrees or fractions thereof, scaled and interpolated where necessary. The size of the products at higher resolutions requires that they be aggregated in subsets of global coverage. Global standard products use the Equirectangular map projection, also known as Simple Cylindrical, while the higher-resolution products afforded by dense polar coverage use the Polar Stereographic projection.
The resolution of equirectangular pixels is in powers of two pixels per degree of longitude and latitude (e.g. 4, 16, 64, 128, 256, 512, and 1024). The resolution of polar projected pixels is in integral numbers of meters at a radius of 1,737,400 m, true at the pole. The pole is a point surrounded by the four central pixels, and the colatitude of a pixel at a distance r meters from the north pole is simply 2arctan(0.5r/1,737,400). Polar stereographic projections are produced at latitudes from 45 degrees to the poles.
Equirectangular map-projected digital elevation models
|
Product |
Pixel size (latitude) |
Number/size of tiles |
Bits per pixel |
|
LDEM_4 |
7.5808 km |
Global, 0-360 |
16 |
|
LDEM_16 |
1.895 km |
Global, 0-360 |
16 |
|
LDEM_64 |
0.4738 km |
Global, 0-360 |
16 |
|
LDEM_128 |
0.2369 km |
Global, 0-360 |
16 |
|
LDEM_256 |
118.45 m |
4 tiles, longitudes 0:180:360 by N/S |
16 |
|
LDEM_512 |
59.225 m |
Longitudes 0:90:180:270:360 by 45° latitude bands |
16 |
|
LDEM_1024 |
29.612 m |
Longitudes 0:30:60:90:120:150:180:210:240:270:300:330:360 by 15° latitude bands |
16 |
Selection of polar map-projected digital elevation models, N/S
|
Product |
Dimensions |
Pixel size |
Latitude range |
Bits per pixel |
|
LDEM_45S_100M |
28880 x 28800 |
100 x 100 m |
+/- 45° to pole |
16 |
|
LDEM_60S_60M |
31040 x 31040 |
60 x 60 m |
+/- 60° to pole |
16 |
|
LDEM_75S_30M |
30496 x 30496 |
30 x 30 m |
+/- 75° to pole |
16 |
|
LDEM_80S_20M |
30400 x 30400 |
20 x 20 m |
+/- 80° to pole |
16 |
|
LDEM_85S_10M |
30336 x 30336 |
10 x 10 m |
+/- 85° to pole |
16 |
|
LDEM_875S_5M |
30336 x 30336 |
5 x 5 m |
+/- 87.5° to pole |
16 |
Additionally, there is one product which is projected into the dynamically defined Principal Axis coordinate system for consistency with all lunar gravity spherical harmonic models. The product is named LDEM_64_PA.IMG, with its corresponding label file.
LOLA GDRDEM global products have the following file names:
productsuffix
where:
product = product name above
suffix = file type/extension
_FLOAT.IMG = floating point image file
_FLOAT.LBL = detached PDS label
.IMG = image file
.LBL = detached PDS label
.JP2 = JPEG2000 file
_JP2.LBL = detached PDS label
LOLA GDRDEM regional products have the following file names:
product_mmmd_nnnd_www_eeesuffix
where:
product = product name above
mmm = minimum tile latitude in degrees
d = direction of minimum latitude
N = north
S = south
nnn = maximum tile latitude in degrees
d = direction of maximum latitude
N = north
S = south
www = westernmost longitude in degrees
eee = easternmost longitude in degrees
suffix = file type/extension
_FLOAT.IMG = floating point image file
_FLOAT.LBL = detached PDS label
.IMG = image file
.LBL = detached PDS label
.JP2 = JPEG2000 file
_JP2.LBL = detached PDS label
In ODE, GDRDEM products have one of the following product IDs:
PRODUCT (images and JPEG2000s)
PRODUCT_MMMD_NNND_WWW_EEE (regional images and JPEG2000s)
PRODUCT_FLOAT (floating point images)
PRODUCT_MMMD_NNND_WWW_EEE_FLOAT (regional floating point images)
Note: Conversion from Digital Number to HEIGHT i.e. elevation in meters, is:
HEIGHT = (DN * SCALING_FACTOR).
The conversion from Digital Number to PLANETARY_RADIUS in meters is:
PLANETARY_RADIUS = (DN * SCALING_FACTOR) + OFFSET,
where OFFSET is the radius of a reference sphere.
The planetopotential TOPOGRAPHY is:
PLANETARY_RADIUS – GEOID_RADIUS,
where GEOID_RADIUS is derived from a gravitational equipotential model.
By convention, the average GEOID_RADIUS at the equator is OFFSET.