The identification of ecological analogs of natural vegetation and food crops using ERTS-1 imagery is discussed. Signatures of four natural vegetation analogs have been determined from color photography. Color additive techniques to improve the photointerpretation are examined. Tests were conducted at test sites in Louisiana, California, and Colorado

Poulton, C. E.

Welch, R. I.

English

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Paper A 6 
AN INTERREGlONAi ANALYSIS OF NATURAL VEGETATION 
ANALOGUES USING ERTS-1 IMAGERY 
Charles E. Poulton and Robin I. Welch, EaPh Satellire Corporaticn, 
2150 Shattuck Avenue, Berkeley, Celifornia M704 
ABSTRACT 
We are seeking t o  determine i f  ecological analogues o f  
natural vegetation and a key food crop, r ice,  have su f f i c i en t l y  
analogous signatures to  be in ter reg ional ly  and, potent ia l ly ,  
g loba l ly  ident ic iab le  from ERTS-1 imagery. I n  the proper 
seasons, r i c e  does have a unique signature i n  one o f  odr tes t  
s l tes  and we have iden t i f i ed  w i th in - f ie ld  var ia t ion that i s  
production related. We have also demonstrated unique sigqa- 
tures fo r  four natural vegetation analogues from color p r i n t s  
and are developing some promising co lor  addi t ive  analy t ica l  
techniques to support t h i s  a ~ d  other projects. Even t h i s  
l imi ted progress i s  encouraging w'th respect to  f e a s i b i l i t y  
of a uniform ecological inventory o f  vegetational resources 
f r c  ERTS imagery. 
Space-acqui red imagery has made i t  possible and pract ica l  t o  inven- 
tory  and monitor vegetational resources i n  the global context. Fu l l  
rea l izat ion o f  t h i s  po teq t i a l i t y  requires three things i n  addi t ion t o  
the imaging capabi l i ty .  F i r s t  i s  a vegetational resources c lass i f i ca t ion  
concept that i s  log ica l  and that can be maintained i n  synoptic treatment 
across p o l i t i c a l  and ju r i sd ic t iona l  boundaries. I n  contrast t o  estab- 
l ished c lass i f ica t ions o f  the plant geographer and plant ecologist, a 
usable c lass i f i ca t ion  must a lso be compatible w i th  the requirements f o r  
in terpreta t ion o f  remotely sensed ikl~ges, including the concept o f  
mult istage inventory. Ecr~nd  !s the dtttrzInat!=::  =f thc Intcrragionol?y 
eppl icable vegetat l o n a l ~ t u r e s  that  can be used t o  i d rn t  i f y  image 
areas i n  t h i s  context. This requires i den t i f i ca t i on  o f  the characteris- 
t i c s  o f  the signatures o f  each analogue and deten. ia t  ion of the extent 
t o  which each signature car - *  extrapolated f o r  appl icat ion i n  regional, 
interregional, and tvent:al. ; j loba l  inventories. This knowledge should 
permit optimum use and ms~ic.;m benef i t  from in terpreta t ion c r i t e r i a  
https://ntrs.nasa.gov/search.jsp?R=19730019482 2020-03-17T09:05:00+00:00Z
developed i n  one region o f  the globe as i t  i s  used i n  image analysis o f  
a3rocl imatolcgical ly analogous regions eisewhere. The t h i r d  requirement 
i s  the determination o f  image in terpreta t ion procedures essential to  the 
recognl t i o n  and mapping of vegetational analogues by use o f  the in ter -  
act ive system o f  space and a i r c r a f t  imagery wi th  huran knowledge and 
ski 1 Is. 
To help meet these requirements, we have selected twn pa i rs  o f  i n te r -  
regional tes t  s i tes  i n  the United States. One pa i r  (Southern Louisiana 
and In te r io r  Valley Cal i fornia) i s  f o r  the study o f  a key fo3d crop ana- 
logue and the other pa i r  (colorado Plateau and Sierra-Lahontati) f o r  
natural vegetational analogues. i n  t h i s  ERTS-I Symposium, we are report- 
ing prel iminary resul ts re la t ing  to  requirements one and two above. Our 
concern ~ i t h  requirement three i s  minimal t o  t h i s  point  i n  time. 
One o f  our analogues i s  the world-important food crop, r ice.  
De f in i t i ve  work on t h i s  analogue w i l l  s t a r t  w i th  the 1973 growing season. 
From ERTS-1 imagery i n  July and September, 1972, we have made some mean- 
ingfu l  observations i n  the Cal i forn ia  tes t  area. Among crops i n  t h i s  
area, r i c e  does have a highly unique, pre-ripening signature i n  the 
color reconstituted ERTS-I data. It appears that  h ig>ly accurate iden- 
t i f i c a t i o n  w i l l  be poss~ble .  We have also determined that some within- 
f i c l d  va r ia t ion  can be detected d i r e c t l y  from the ERTS imagery a t  opera- 
t i ona i l y  fessible, color reconstituted scales. In  t h i s  instance, we are 
seeing the ground-confirmed influence o f  s o i l  sa l i n i t y .  This i s  an 
example o f  one o f  the negative production factors that  w i l l  be used i n  a 
procedure we have developed for y i e l d  predict ion. 
A i r c ra f t  photography i s  an integral  par t  o f  these predict ions. 
H ighf l ight  provides the second stage i n  mult istage sampling. The higher 
resolut ion enables both refinement of del ineation and i den t i f i ca t i on  o f  
other more elusive y ie ld-  i n f  luenci ng environmental factors as evidenced 
i n  p i an i  srcr~th.  
Now turning t o  the natural vegetation component o f  our investiga- 
t ion, i n  theory and i n  fac t ,  no two stands o f  vegetation are ident ica l ;  
but i n  sp i te  o f  t h i s  seeming dilemma, we have an operational legend 
system that meets previously mentioned requirements one and two. I f  one 
concentrates a t tent ion on i h t  s im i l a r i t i e s  instead o f  the differences 
and considers the plant cornunity as a whole rather than as indiv idual  
economic species, h ighly usefcl  c lass i f ica t ions are possible. It i s  
well  established by plant socic logists and ptant geographers that  the 
concept o f  vegetatlonal analogues Is val id .  Demonstration o f  the degree 
of ana!ngy Is d~penu'efii ~n the c iassi  t i ca t  ion c r i t e r i a  used and on the 
recognition o f  h ierarch ica l ly  comparable levels i n  the c l ass i f i ca t i on  
scheme. With special a t ten t ion  t o  tk- needs o f  ERTS interpretat ion,  we 
have adapted a un'gorm ecological legend system i n i t i a l l y  devised by my 
graduate students and me a t  Oregon State University t o  the needs o f  t h i s  
project .  I t  i s  a devisive system i n  which the three broadest hierarchi-  
cal levels are based on physiognomic and struct t i ra l  character ist ics o f  
the vegetation. The four th  level i s  based on f : o r i s t i c  c r i t e r i a ,  gener- 
a l l y  a t  generic level. The more ref ined i i ? ra r ch i ca l  levels below t h i s  
are based on p lant  sociological c r i t e r i a  and are best developed by 
agglomerative c lass i f i ca t ion  methods (~oul tor . .  1972). 
In  t h i s  study, we are not considering these l a t t e r ,  h ighly ref ined 
classes because they are general ly not ident i f i ' ib le from space imagery 
except through associated and convergent evident?. In  general, as one 
moves from the local  to  the regional, to  the continental, and t o  the 
global scene, ecological analogues are demo~c,trable only by moving up 
the hierarchical  c l ass i f i ca t i on  t o  broader genera:izations. The problem 
of interprer ing analogous vegetations from remotely sensed imagery 
requires that  we f i r s t  determine the level  i n  the hierarchical  legend 
that i s  appropriate t o  the scale, resolution, and discr iminat ing power 
o f  each system. Our work on interregional  analogues i s  helping t o  define 
these legend levels f o r  the ERTS-I system. 
We have been approaching the study o f  natural vegetation analogues 
by working w i th  the black and white photo images u n t i l  as recently as 
l as t  week. We have iden t i f i ed  a group o f  analogues that  are candidates 
f o r  interregional  comparison (See Type I1 Report, Poulton and Welch, 
31 January 1973). We have j u s t  made a f i r s t  andlysis o f  intra-regional 
repeatab i l i ty  o f  some o f  these signatures i n  the color reconstituted 
product from an !ZS Addcol. By ca re fu l l y  set t ing the lamp in tens i ty  
d i a l s  t o  the same set t ing f o r  each separate scene, f i d e l i t y  of the color 
reconstituted signature f o r  many vegetational analogues was very good 
among scenes and upon reset t ing o f  ident ica l  scenes. 
I n  studying these image areas, i t  i s  imed ia te ly  obvious that  many 
of us who are concerned about in terpreta t ion o f  natural vegetation w i l l  
face two contrasting s i tuat ions,  each w i t h  i t s  own unique solution. 
These si tuat ions are: 
1)  I n  subhumid and humid areas, vegetation density i s  
su f f i c i en t  to  pr imar i ly  determine image character ist ics.  
2) I n  some semi-arid condit ions and pa r t i cu l a r l y  i n  a r i d  
envi ronments, sparsi t y  o f  vegetation produces an image 
tkt i s  overridden by the nonvegetational features o f  
the subject--by the exposed s o i l  surface. 
In the f i r s t  Instance, the vegetation anal.~guas are d i r e c t l y  in terpret -  
able t o  the extent that  t he i r  images are consistent w i t h i n  and d i f f e ren t  
among analogues. I n  the second case, photo- ident i f ica t ion o f  vegeta- 
t iona l  subjects can be done only from associated and convergent evidence 
rather than by image features that  are related d i r e c t l y  t o  vegetation 
reflectance. We have so f a r  been concerned wi th  s i tuat ions where vege- 
ta t ion  features override the s o i l  background i n  determining image 
character ist ics.  
We have made one set cf  intra-regional comparisons between two 
scenes f o r  analogues o f  dense Douglas f i r/spruce-f i r, oakbrush/aspen, 
juniper, ponderosa pine, sagebrush and sal tsage. The consistency o f  
these images between scenes encourages us t o  expect some interregional 
app l i cab i l i t y  o f  the signatures. The sharpness of color image separa- 
t ions of a l  i these analogues except the oakbrush/aspen aed the sagebrush/ 
saltsage a lso suggests that 2ur experimental hypothesis i s  sound and 
that benef i ts w i  l I, therefore, accrue from the characterization and 
iden t i f i ca t ion  of analogous signatures i n  one region for use i n  another 
if the regions are i n  fac t  vegetat ional ly analogous. Our work plan now 
c a l l s  for  quant i f ica t ion and a more systematic comparison o f  photo image 
character ist ics f o r  ecalogical analogues and study o f  image consistency 
and i d e n t i f i a b i l i t y  among scenes between regions and over time. It may 
bc that some analogues not i den t i f i ab l e  i n  these single, late-sumner 
scenes w i l l  have a unique mult idate signature. 
Especially t o  investigate these kinds of phenomena as wel l  as 
changes i n  the resource over time, Phi l  Langley o f  our Berkeley Of f ice 
has been experimenting wi th  special op t i ca l  enhancement techniques by 
color combining bot5 pos i t i ve  and negative f o r  the same scene and date 
and by successfully rcg is ter ing among dates. By combining pos i t ives o f  
bands 5 and 7 f o r  July u i t h  a pos i t i ve  and a negative o f  band 7 o f  the 
same scene f o r  October, he has been able t o  produce strong color con- 
t ras ts  i n  areas o f  change. These included generation of a unique color 
for  changes i n  agr i cu l tu ra l  crops between the two dates, detection of 
areas o f  deciduous hardwoods, separation o f  north-slopes supporting 
Douglas f ir /Sugar pine vegetation, and the v i v i d  detection o f  changes 
i n  the areas o f  lakes. We expect that  techniques l i k e  these w i l l  f i n d  
usefulness I n  a l l  o f  our par t i c ipa t ing  projects where vegetation i s  the 
subject of concern. 
A i r c ra f t  photography i s  an in tegra l  pa r t  o f  our a. sase. The 
procedure i s  t o  p l o t  a i r c r a f t  h i gh f l i gh t  l ines on the I:I,GOO,OQO ERTS 
imagery and then s t r i v e  t o  locate a l l  ca l ib ra t ion  s i tes  i n  these s t r ips .  
The designation o r  mapping o f  unique images on the h igh f l  ight  serves as 
an intermediate "ground t ru th t t  f o r  ERTS in terpreta t lon and wi 11 be an 
essential component o f  the system where the analogue signatures are t o  
be used i n  a mult istage inventory of natural vegetation o r  food crop 
resources. The a i r c r a f t  photography o f ten  helps to LL.XP!B!:: a;i~,s: les 
I n  the EATS imagery where vegetation patterns are in t r i ca te ,  I n  addi- 
t ion, we have taken low oblique photos over a l l  tes t  areas as an addi- 
t i ona l  a i d  to  image identification and subject characterization. 
The fo l l ow ing  i s  our assessment o f  bene f i t  from p ro jec t  a c t i v i t y  
t o  date: We have confirmed the advantages o f  i n t e r p r e t i n g  the ERTS i n  
stereo wherever s ide- lap permits. This i s  p a r t i c u l a r l y  he lp fu l  when 
r e l a t i n g  vegetat ion t o  landforms, espec ia l l y  i n  semi-arid and a r i d  env i r -  
onments o r  where conf i rmat ion o f  major e levat iona l  re la t ionsh ips  i s  
important t o  the i d e n t i f i c a t i o n  decision. 
From pre l im inary  work w i t h  the r i c e  i d e n t i f i c a t i o n  problem, we f e e l  
tha t  use o f  ERTS imagery together w i t h  a i r c r a f t  subsampl ing w i  1 l lead 
t o  e f f i c i e n c i e s  a t t r i b u t a b l e  t o  the space imagery i n  est imat ing acreage 
and production o f  t h i s  key world food crop. 
The capabi l i t y  t o  provide a uniforli l  synopt ic  treatment o f  vegeta- 
t i o n a l  resources i r respec t i ve  of ownerships, agency j u r i s d i c t i o n ,  and 
p o l i t i c a l  boundaries br ings w i t h i n  our grasp a nation-wide system o f  
uniform ecological  inventory and rnon~tor;ng o f  our e n t i r e  vegetat ional  
resource base. Because o f  ERTS, t h i s  could now be nearing feasi  b i  l i t y  
i n  a context not a t t a inab le  from the myriad o f  use- and product-biased 
legend systems and inventory methods used by the many Federal and s ta te  
agencies concerned w i t h  vegetat ional  resources of our country. 
To the extent  t ha t  in te r reg iona l ,  and eventual ly  g lobal ,  vegetzt ion 
analogues can be demonstrated and t l ie i  r d i f f e r e n t i a t i n g  image features 
defined and characterized, we w i l l  g r e a t l y  enhance the value and i n t e r -  
p r e t a b i l i t y  o f  ERTS imagery. Our work t o  date has encouraged us i n  the 
f e e l i n g  tha t  the approach we are using w i l l  s i g n i f i c a n t l y  reduce the 
eventual cost  o f  ground-truth work as progress on the nat ional ,  con t i -  
nental,  and g lobal  assessment of vegetat ional  resources and key food 
crops i s  ca r r i ed  out- -hopeful ly  w i t h  a f u l l y  operat ional  s a t e l l i t e  
imaging system. 
LITERATURE CITED 
Poulton, Charles E. 1972. A comprehensive remote sensing legend systen 
f o r  the ecological  charac ter iza t ion  and annotat ion o f  natura l  and 
a l  tered landscapes. Oregon Agr i c u l  t u r a l  Experiment Stat  i on  Techni- 
c a l  Paper No. 3435. In: Proceedings, 8 t h  In ternat iona l  Symposium 
on Remote Sensing o f  Environment, Ann Arbor, Michigan, October 2-6, 
1972. 


An interregional analysis of natural vegetation analogues using ERTS-1 imagery

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