Cloud-free imagery covering the Tucson, Ariz., region for the period from August 22 to November 2, 1972, was used to determine the utility of ERTS-1 data for discriminating boundaries between plant communities. The following studies were made from imagery analyzed by use of an Electronic Satellite Image Analysis Console: (1) console-generated color composites from MSS-5 and MSS-6 bands were recorded photographically from the console color monitor. The color photographs were then used to compare with short-term changes in vegetative cover observed on the ground; (2) using the console, microdensitometric traces were made along selected traverses to quantify changes in scene irradiance across the image field; (3) quantitative plant coverage data, collected at ground-truth stations along the traverses, were compared with the densitometric values

Turner, R. M.

English

NASA Technical Reports Server

Paper rN 7 
USE OF THE 5RI ELECTRONIC SATELLITE IMAGE ANALYSIS CONSOLE FOR 
MAPPING SOUTHERN ARIZONA PLANT COMMUNITIES FROM ERTS-1 
IMAGERY 1 
Raymond M .  Turner, U. S. Geological Survey, Tucson, Arizona 
ABSTRACT 
Cloud-free imagery cov:ering the  Tucson, Ar i z . ,  regior. f c r  
t h e  period from August 22 t o  November 2 ,  1 9 7 2 ,  was used t o  de t e r -  
mine t h e  u t i l i t y  of E R T s - 1  da t a  f o r  d i scr imina t ing  boundaries 
between p l an t  communities. 
The following s tud i e s  wer,e made from imagery analyzed by 
use of Stanford Research I n s t i t u t e ' s  E lec t ronic  S a t e l l i t e  image 
Analysis Console: 
( I )  Conscle-generated co lo r  composites from M5S-5 and 
MSS-6 bands were recorded photographical ly from t h e  
console co lo r  monitor.  The co lo r  photographs were then 
used t o  compare with short-term changes i n  vegeta t ive  
cover observed on t h e  grounl .  
( 2 )  Using t h e  c o ~ s o l e ,  microdensitometric t r a c e s  were 
made along se l ec t ed  t r a v e r s e s  t o  quant i fy  cLanges i n  
scene i r r ad i ance  across  t h e  image f i e l d .  YSS-6 minus 
MSS-5 densitometry values were employed a s  a r e l a t i v e  
measure of p l an t  cover i n  t h e  wide range of vege ta t ive  
zones covered by t h e  t r a v e r s e s .  
( 3 )  Quant i ta t ive  p l an t  coverage d a t a ,  co l l ec t ed  a t  
ground-truth s t a t i o n s  along t h e  t r a v e r s e s ,  were com- 
pared with t h e  dens i tomet r ic  values.  
The U.S. Geoiogical Survey i s  engaged i n  a program aimed a t  mapping 
southcrn Arizona vegeta t ion  from ERTS-1 imagery. This r epo r t  descr ibes  
prel iminary r e s u l t s  i n  which both t ime- lapsez  color-cornposited imagery 
and microdensitometry a r e  used t o  d e l i n e a t e  and i d e n t i f y  p l an t  communi- 
t i e s .  The imagery was analyzed on t h e  E lec t ron ic  S a t e l l i t e  Image Analy- 
sis Console a t  Stanford Research I r , s t i t u t e ,  Menlo Park, C h l i f . ,  and I 
wish t c  acknowledge t h e  important con t r ibu t ion  of SRI s c i e n t i s t s ,  
e spec i a l l y  Wm. E .  Evans a ~ d  S. M .  Serebreny. 
1/ P u b l i c a t i o n  a u t h o r i z e d  by t h e  D i r e c t o r ,  U . S .  G e o l o g i c a l  S u r v e y .  
- 
761 
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https://ntrs.nasa.gov/search.jsp?R=19730019553 2020-03-17T08:46:17+00:00Z
Detai led mapping of a r i d  region vegeta t ion  using s a t e l l i t e  imagery 
depends upon de t ec t ing  d i f f e r ences  i n  t h e  timing of p l an t  grcwth a c t i v l - y  
among t h e  communities comprising t h e  r eg ion ' s  vege ta t ive  mosiac. The 
short-term r e p e t i t i v e  viewing c a p a b i l i t y  of t h e  ERTS s e r i e s  s a t e l l i t e s  
provides an e s p e c i a l l y  fo rce fu l  means f o r  performing t h i s  t a s k .  In  a r i d  
sub t rop ica l  regions with wide e l eva t iona l  d i f f e r ences ,  such a s  southern 
Arizona, t he  var ied  environment g ives  r i s e  t o  d iverse  p l an t  growing 
regimes. Among t h e  kinds of p l a n t s  present  a r e  those  t h a t  a r e  evergreen 
(such as p ines  end l i v e  oaks a t  higher  e l eva t ions  o r  c reosote  bush a t  
lower e l eva t ions )  and those  t h a t  a r e  green only seasonal ly .  Among t h e  
l a t t e r  a r e  win ter -ac t ive  spec ies  (ephemeral g r a s se s  and fo-bs) and 
summer-active spec i e s  (perennia l  and ephemeral g r a s se s  and ephemeral 
fo rbs ) .  A t  lower e l eva t ions  where t h a  dominant pt.rd;v.;al p l a n t s  tend t o  
be widely spaced, d i s t i ngu i sh ing  one open commurity from another  would 
be d i f f i c u l t  i f  it were not  f o r  t h e  temporari ly dense growths of t h e  
small ephemeral spec i e s  t h a t  appear during seasons of favorable r a i n f a l l .  
Where such p l a n t s  with d i s t i n c t i - ~ e  per iods  of f o l i a t i o n  grow densely 
enough t o  be de tec ted  by t h e  r e l a t i v e l y  low-resolution systems of  
s a t e l l i t e s ,  it should be poss ib le  t o  employ seasonal  growth d i f f e r ences  
t o  map t h e  a r e a s  they  occupy. 
Of bas ic  i m p o r t a x e  t o  our  approach is  t h e  unique manner i n  which 
green p l an t  t i s s u e s  respond t o  t h e  wavelengths sensed by rhe  ERTS-1 
mul t i spec t r a l  scanner. Our e f f o r t s  t o  da t e  have r e l i e d  heavi ly  on t h e  
d i f f e r ences  i n  p l a n t  r e f l ec t ance  between t h e  MSS band 5 and t h e  MSS band 
6. In t h e  MSS-5 s p e c t r a l  range (0.6 t o  0.7 micrometers) p l a n t s  r e f l e c t  
l i t t l e  energy; through t h e  MSS-6 range (0.7 t o  0.8 micrometers) they 
i r r a d i a t e  s t rong ly .  Although l ea f  i r r ad i ance  i n  t h e  two bands is  i n f l u -  
enced by sepa ra t e  systems, one having t o  do with l e a f  pigment c h e r i s t r y  
and t h e  o the r  with l e a f  anatomy, both systems a r e  c lo se ly  r e l a t e d  t o  t h e  
quant i ty  of  f o l i a g e ,  t h e  va r i ab l e  t h a t  we a r e  at tempting t o  d e t e c t .  
METHODS 
ERTS-1 mul t i spec t r a l  sccrrner bulk imagery i n  70-mm t :Tat f o r  t h e  
Tucson, Ariz.,  reg ion  was used i n  t h i s  s tudy,  During t h e  :reliminary 
period covered by t h i s  r e p o r t ,  use of MSS bands E and 6 wus emphasized. 
Diaposi t ives of  cloud-free scenes were employed throughout.  Use was 
made p r i n c i p a l l y  of  image numbers 1.030-17271-5 and 1030-17271-6 f o r  
August 22, 1972, and numbers 1102-17280-5 and 1102-17280-6 f o r  November 
2, 1972. 
A s  one approach, microdensitometry was sarformed by t h e  console 
acrose two east-wart  t r ave rees  (Fig.  1 ) .  Each t r a v e r s e  was f o u r  coneole 
TV l i n a r  wide, r ep re ren t ing  , f o r  t h e  magnif icat ion ured , about 800 
meterr on t h e  ground. Scenr i r r ad i ance  va luer  along t h e  fou r  p a r a l l e l  
t r a v e r r a s  were measured and averaged f o r  t h e  MSS-5 and MSS-6 imager. 
The MSS-5 values were rubt rac tad  from t h e  MSS-6 va luer ,  and t h c  r c r u l t i n g  
d i f f e r ences  as seen by t h e  t r d c e s  on t h e  console osc i l loscope  were com- 
pared with an e leva t ion  p r o f i l e  and known vegeta t ion  p a t t e r n s  f o r  t h e  
t r a v e r s e s .  To assure  image-to-image and date- to-date uniformity,  den- 
s i t ome t r i c  readings were f i r s t  made ac ros s  t h e  grey s c a l e  on each image; 
adjustments were then made on t h e  console t o  produce comparable curves 
of vol tage versus grey s t e p  number f o r  a l l  scenes.  Following t h i s  ad- 
justment, a given grey l e v e l  r ep re sen t s  t h e  same amount of r e f l e c t e d  
energy on a l l  scenes.  
In  a second a n a l y s i s ,  p l an t  coverage was measured a t  roughly 18-day 
i n t e r v a l s  a t  f i g e  s i t e s  along two add i t i ona l  t r a v e r s e s ,  t h e  S i e r r i t a  
Mountain and Mile Wide Road t r a n s e c t s  (Fig.  1 ) .  The measurements, made 
as c lose  t o  t h e  day of t h e  s a t e l l i t e ' s  imaging o v e r f l i g h t s  a s  f e a s i b l e ,  
were gathered from rep re sen ta t i ve  open communities of t h e  d e s e r t  and of 
t h e  grassland borderixg t h e  d e s e r t .  Changes i n  measured p l an t  coverage 
a r e  shown i n  f i g u r e  2 f o r  t h e  period from October 1972 through January 
1973, with ex t r apo la t i ons  made through t h e  remainder of  t h e  twelve 
months. These curves show a c t u a l  changes and an t i c ipa t ed  changes i n  t h e  
amount of green f o l i a g e  covering t h e  s o i l  su r f ace .  The hypothe t ica l  
p ro jec ted  changes a r e  shown only t o  i l l u s t r a t e  how r e p e t i t i v e  imagery 
may be used f o r  i den t i fy ing  p l a r t  communities. The a c t u a l  changes i n  
9 l an t  cover were compared with MSS-6 minus MSS-5 dens i tomet r ic  t r a c e s  
along only t h e  S i e r r i t a  Mountain t r a n s e c t .  This  a n a l y s i s  was performed 
on ap enlarged view of p a r t  of t h e  same images as noted above. The 
t r a v e r s e  used f o r  dens i tomet r ic  a n a l y s i s  was fou r  scan l i n e s  wide repre-  
sen t ing ,  at  t h e  magnif icat ion se l ec t ed ,  a width ci about 250 meters  on 
t h e  ground. 
In t h e  t h i r d  a n a l y s i s ,  add i t i ve  c o l o r  d i sp l ays ,  using two primary 
co lo r s ,  were recorded photographical ly from t h e  console 's  c o l o r  monitor.  
A s  before MSS bands 5 and 6 were employed. Cyan was pa i red  with MSS-5 
and red  was pa i red  with MSS-6, providing a p a ~ t i a l  simu1at:on of  f a l s e -  
co lo r  I R  photography. The 35-mm ful l -frame images and an enlarged view 
of an a r ea  support ing a heavy g ~ o w t h  of  phreatophytes were analyzed f o r  
q u a l i t a t i v e  scene changes t h a t  can be used t o  map vegeta t ion  and t o  
es t imate  t h e  amount of p l an t  f o l i a g e .  
RESULTS 
Densitometric studies.--In f i g u r e  3 may be seen t h e  changes i n  
scene i r r ad i ance  ac ros s  t h e  Old Baldy Transect  from t h e  v i c i n i t y  of t h e  
Baboquivari Mountains on t h e  west t o  t h e  Mule Mountains on t h e  e a s t ,  a 
d i s t ance  of 170 ki lometers .  The osc i l loscope  t r a c e  g ives  t h e  va lues  ob- 
t a ined  when MSS-5 scene i r r ad i ance  is sub t r ac t ed  from MSS-6 scene i ~ r a d -  
iance.  The images used were f o r  August 22 ,  1972 (numbers 1030-17271-5 
and 1030-17271-6). The d i f f e r ence  curves r e s u l t i n g  f ~ o m  t h i s  manipula- 
t i o n  vary d i r e c t l y ,  f o r  t h e  most p a r t ,  with changes i n  p l a n t  coverage. 
Patches of dense vegeta t ion  i n  moist h a b i t a t s ,  such as v a l l e y  bottoms 
and high mountains, show t h e  g r e a t e s t  d i f f e r ence  values.  The Santa Cruz 
River va l l ey ,  Old Baldy (Mount Wrightson), Babocomari Creek, and t h e  San 
Pedro River v a l l e y  g ive  t he  highest  va lues  where crossed by t h e  t r a n s e c t  
on t h i s  image. 
In  Zigure 3 ,  t h e  d i f f e r ence  t r a c e  f o r  t h e  Old Baldy Transect  is 
shown f o r  November 2, 1972 (numbers 1102-17280-5 and 1102-17280-6). 
Compa~ed t o  t h e  August 22 t r a c e ,  t h e r e  is  a tendency toward a decrease 
i n  t h e  magnitude of t h e  d i f f e r ence  va lues .  The f l a t t e n i n g  of  t h e  d i f -  
ference curve ind ica ted  by t h e  November t r a c e  occurs  with t h e  end o f  t h e  
summer r a iny  season and t h e  coincident  l o s s  of  f o l i a g e  by t h e  ephemeral 
and deciduous perennia l  p l an t s  a s  they e n t e r  t h e  per iod  of win ter  qu ies -  
cence. La t e r ,  a s  win ter  annuals begin growth i n  response t o  win ter  
r a i n s ,  it i s  a n t i c i p a t e d  t h a t  t h e  d i f f e r ences  w i l l  aga in  increase ,  but  
only f o r  t h e  lower e l eva t ions .  A t  h igher  e l eva t ions ,  where evergreen 
saks  and p ines  dominate, t h e  matr ix of  g ra s se s  and fo rbs  w i l i  remain 
dormant during t h e  win ter  r e s u l t i n g  i n  va lues  t h a t  a r e  somewhat lower 
than those  of  summer. 
I n  f i g u r e  4, d i f f e r ence  t r a c e s  f o r  t h e  Mine Transect  f o r  two d a t e s  
(August 22 and November 2 ,  1972) a r e  shown. A f l a t t e n i n g  of t h e  Novem- 
be r  d i f f e r ence  curve, a s  noted f o r  t h e  Old Baldy Transect ,  can a l s o  be 
seen here. Of p a r t i c u l a r  i n t e r e s t  is t h e  change i n  t h e  curves where t h e  
t r a n s e c t  c ros se s  t h e  extensive grass land  bordering upper Cienega Creek. 
The change is i n t e r p r e t e d  a s  represent ing  a dec l ine  i n  green cover as 
t h e  g ra s se s  e n t e r  t h e  winter  dormant condi t ion .  The low mountains along 
t h e  Mine Transect  have r e l a t i v e l y  low d i f f e r ence  va lues  i n  t h e  win ter  
because of  t h e  spa r se  growth of evergreen t r e e s .  Mesquites, o t h e r  surn- 
mer f o l i a t i n g  shrubs,  and g ra s se s  dominate t he  landscape a t  t h e s e  i n t e r -  
mediate e l eva t ions .  
I n  f i g u r e  5 ,  two d i f f e r ence  t r a c e s  f o r  t h e  S i e r r i t a  Mountain Tran- 
s e c t  f o r  August 22 and November 2 ,  1972 a r e  shown. P lan t  coverage i s  
being measured a t  two s i t e s  ( S i e r r i t a  Mountain 1 and 2, Fig. 2)  along 
t h i s  t r a n s e c t  f o r  comparison with t h e  d i f f e r e n c e  t r a c e s .  (Although 
ground-truth d a t a  are being co l l ec t ed  at  t h r e e  nearby s i t e s  along t h e  
Mile Wide Road Transect ,  densitometry fcr ,h i s  p a r t  c f  ou r  work is in -  
complete and w i l l  no t  be repor ted  upon a t  t h i s  time.) I t  is t o o  e a r l y  
i n  our  program t o  determine how c l o s e l y  t h e  p l a n t  coverage va lues  w i l l  
fol low f l u c t u a t i o n s  i n  t h e  d i f f e r ence  t r a c e s .  A s  expected, t h e  maximum 
d i f f e r ence  va lues  f o r  November a r e  lower than  f o r  August. A t  t h e  po in t  
where t h e  t r a n s e c t  c ros se s  a low a r e a  wi th  dense phreatophyte vegeta t ion  
near  Brawley Wash, t h e  va lues  a r e  low i n  November compared with August 
because t h e  p l a t s  have become l e a f l e s s  by November. Cul t iva ted  f i e l d s ,  
some o f  which are fa l low and some cropped, produce c h a r a c t e r i s t i c  shaxlp 
changes near  t h e  extreme r i g h t  end of  t h e  d i f f e r ence  ems. 
Time-lapse s t u d i e s  o f  co lor -addi t ive  images.--Phreatr>phyte vegeta- 
t i o n  along a s h o r t  reach  of t h e  San Pedro River  near Bason, A ~ i z . ,  and 
i n  an a r ea  a t  t h e  confluence of R i l l i t o  and Sabino Creeks near Tucson 
a r e  being examined i n  d e t a i l ,  Changes i n  t h e  en larged ,  color-composite, 
video images w i l l  be compared with observed changes i n  f o l i a t i o n  among 
the  dominant phreatophyte o r  r i p a r i a n  spec i e s  occupying t h e  s i t e s .  I t  
should be poss ib l e  t o  map t h e  vegeta t ion  of t he se  h a b i t a t s  where dense,  
pure s tands  of t he se  spec i e s  occur. I d e n t i f i c a t i o n  of  t h e  spec ies  
should be poss ib le  by observing t h e  d i f f e r ence  i n  timing of f o l i a t i o n .  
Time-lapse viewing of console-generated, co lor -addi t ive ,  ful l -frame 
ERTS images w i l l  be used t o  cons t ruc t  vege ta t ion  caps covering t h e  main 
s tudy s i t e ,  an a r ea  100 n a u t i c a l  mi les  on a s i d e  with Tucson a t  t h e  ten- 
t e r .  In  compiling t h e  vegeta t ion  map, which is t h e  f i n a l  product of  
t h i s  p r o j e c t ,  scene changes on t h e  mu l t i spec t r a l  images w i l l  be exam- 
ined i n  conjunction with o t h e r  analyses perfcrmed on t h e  E lec t ron ic  
S a t e l l i t e  Image Analysis Console, such a s  co lo r  s l i c i n g ,  scene-to-scene 
d i f fe renc ing ,  and densitometry. 
Figure 1. P a r t  of an ERTS-1 i r  age (1156-17280-5) showing l o c a t i o n  
of t r a n s e c t s  mentioned i n  t h e  t e x t  ( 1  = Mile Vide Road 
Transect ,  2 = S i e r r i t a  Mo~tntain Transect ,  3 = Mine Tran- 
s e c t ,  b = Old Baldy Transect) .  
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Use of the SRI electronic satellite image analysis console for mapping southern Arizona plant communities from ERTS-1 imagery

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