-17 Nov. 1999
6,17,18,19,20 (SDP v2)
levation differences
| Mean Sea Surface
| for ocean tides
resulting elevation data
ct the effects of long
1ge residuals time series
vith a window length of
of ocean surface laser
yas 50, and a 3 sigma
ed. The resulting ocean
oss land areas using a
d after the land. The
the — sla02.bp.surface 3
n error that is primarily
[he geolocation process
ellipsoid. Orthometric
ing the geoid height at
Earth Geoid Model 96
his level of processing
’roduct Version 2 (SDP
CESSING
ding to a scheme that
and surfaces based on
e 5 minute (10 km)
e 4). Ocean and land
valid returns, from the
| returns, due either to a
r a no-range return (no
the range acquisition
defined as those whose
om sea level (elevation
nd surface returns had
rs of TerrainBase. This
chosen to account for
location errors causing
lief errors. This method
of land surface returns,
de clouds as being from
International Archives of Photogrammetry and Remote Sensing, Vol. 32, Part 3W14, La Jolla, CA, 9-11 Nov. 1999
the surface. Returns classified as clouds included those more
than 500 m and 20 m above the TerrainBase and ocean
reference surfaces, respectively, and below 10,000 m
(considered to be the limit for cloud formation). Returns
classified as noise included those 500 m and 20 m below the
TerrainBase and ocean reference surfaces, respectively, or
above 10,000 m. Figure 4 shows a histogram of the various
classification categories for the approximately 2.1 million laser
shots that have been geolocated.
orientation for each laser vector. The orientation is
characterized by the vector's azimuth (horizontal angle of its
projection with respect to North) and angle off-nadir (zero in
the nadir pointing position), provided in the sla02.pap.azimuth
and sla02.pap.aoffnadir parameters of the sla02 structure.
Caution should be used when interpreting the values provided
for the no-range data, since the geolocation information
associated with these is not valid.
SLA-02 Return Types
Obs.: 1,2,3,4,4a,7,8,9,10,11,12,13,15,16,17,18,19,20
587,172 over-land pulses (28%)
1511,828 over-ocean pulses (72%)
600,000
Surface returns within +-500m of TerrainBase elevation (S'grid) elevation Ocean Shots
A es N Ee
Cloud returns between 500m above TerrainBase and 10 000m
500.000 1... anal SL SLD BEL oh Jl oe bets eit pn me Ama ne N amer
Noise retums more than 500m bellow TerrainBase or above 10 000m
350.000 4--7—------r-[ 00: 020 0n eut teni dna om imme mi mmm in mi I RY om re
Mo range pulses have no return signal above detection threshold
400.000 TERE AP IW rr Tr ARIE CIEE os eI TR
e
S iD ee EEE een e rm
3 NS
d 300,000 1... nz NN DT No
2
= 250,000 +-------------------------------"- #22 NNSSSSNNNE 7777 A RY === = -
* Land Shots
200,000 |------------------------------- A NNNNNNNNN. 77777 NNSSSSSNINNNNNNNNN| 77777
150,000 + --------------------------------- É ANNE - - - - - ANNNNNNNNN-- - - - -
100,000 + NN -------- cene
50,000 - N N inus
No range Noise Clouds Surface | No range Noise Clouds Surface
22.32% 3.20% 16.30% 58.18% 24.49% 4.08% 3426" 37.169
% of land total % of ocean total
Fig. 4 Number of occurences of SLA-02 return types for all observations processed
The proportion of non-valid returns (noise and no range) was
comparable for land and ocean surfaces. The proportion of
cloud returns is significantly lower for the land as compared to
the ocean, indicative of anomalous, sparse cloud cover over the
land areas sampled during the mission. ^ Environmental
parameters are also provided in the SLA-02 data set, including
ISLSCP land cover class and Normalized Difference
Vegetation Index (NDVI), to provide a context for the derived
bounce-point geolocation.
32. Orientation of the Laser Vector
To allow assessment of off-nadir pointing effects on pulse
spreading of the backscatter return, the orientation of the laser
vector with respect to the Earth’s surface is reported. Once the
altimetry data were geolocated, the bounce point topocentric
coordinates and shuttle position were used to compute the
4. PROCESSING OF RETURN BACKSCATTER
ENERGY
Methods used for the analysis of waveforms acquired during
the second flight of the Shuttle Laser Altimeter (SLA) are
summarized here. They represent modifications made to codes
developed for SLA-O1. SLA waveform processing is
implemented in the Interactive Data Language (IDL)
environment. The methods are dynamic and continue to be
modified as experience is gained. Therefore, the following
procedures reflect the current SLA ‘state-of-the-art’ processing.
Further discussion of the procedures is described in the
documentation distributed with the data set, and we refer the
reader to it for more details on the subject.
e
