Coastal vegetation species appearing in the ERTS-1 images taken of Delaware Bay on August 16, and  October 10, 1972 have been correlated with ground truth vegetation maps and imagery obtained from high altitude RB-57 and U-2 overflights. The vegetation maps of the entire Delaware Coast were prepared during the summer of 1972 and checked out with ground truth data collected on foot, in small boats, and from low-altitude aircraft. Multispectral analysis of high altitude RB-57 and U-2 photographs indicated that five vegetation communities could be clearly discriminated from 60,000 feet altitude including: (1) salt marsh cord grass, (2) salt marsh hay and spike grass, (3) reed grass, (4) high tide bush and sea myrtle, and (5) a group of fresh water species found in impoundments built to attract water fowl. All of these species are shown in fifteen overlay maps, covering all of Delaware's wetlands prepared to match the USGS topographic map size of 1:24,000

Bartlett, D. S.

Daiber, F. C.

Klemas, V.

English

NASA Technical Reports Server

Paper E 8 
IDENTIFICATION OF MARSH VEGETATION AND COASTAL LAND USE IN 
ERTS-1 IMAGERY 
V. Klernas, F. D a ~ b e r  dnd D. Bart let t ,  College of Marine Stud~es, Uriiversity of 
Delaware, Newark, Delaware 197 7 1 
ABSTRACT 
Coastal  vege t a t i on  spec i e s  appearing i n  t he  ERTS-1 images taken 
of Delaware B;>.y on August 16, and October 10,  1972 (Observation I . D .  
Nos. 1024-15073 and 1079-15133) have been c o r r e i a i e d  ~ i t h  ground truch 
vege t3 t ion  maps and imagery obtained from h igh  a l t i t u d e  RB-57 and 
&-2 c v e r f l i g h t s .  The vege t a t i on  maps of t he  e n t i r e  Delaware Coast 
were prepared during t he  summer of 1972 and checked ou t  wi th  ground 
t ru th  da t a  co l l ec t ed  on f o c t ,  i n  small  b o a t s ,  and from low-al t i tude 
a i r c r a f t .  Mu l t i spec t r a l  a n a l y s i s  of high a l t i t u d e  RB-57 and U-2 
photographs i nd i ca t ed  t h a t  f i v e  vege t a t i on  co~nmunities could be  
c l e a r l y  d i sc r imina ted  from 60,000 f e e t  a l t i t u d e  inc luding ,  1 )  s a l t  
marsh cord grass  (Spar t ina  a l t e r n i f l o r a ) ,  2)  s a l t  marsh hay and sp ike  
grass  (Spar t ina  pa t ens  and D i s t i c h l i s  s p i c a t a )  , 3) reed  g ra s s  
(Phragmites - c o m u n i s ) ,  4) h igh  t i d e  bush and s e a  myr t le  (* spec ies  
Baccharis hal imifol ia_) ,  and 5) a  group of f r e s h  water  spec i e s  found i n  
impoundments b u i l t  t o  a t t r a c t  water  fowl. A l l  of t he se  spec i e s  a r z  shown 
i n  f i f t e e n  over lay  maps, covering a l l  of Delaware's wetlands prepared t o  
match t h e  USGS topographic map s i z e  of 1 :24 ,000 .  
Najor co rnun i t i e s  of I) Spa r t i na  a l t e r n i f  l o r a ,  2) Spa r t i na  pa tens  
and D i s t i c h l i s  s p i c a t a ,  and 3) -- Iva  frutescens- and Baccharis h a l i m i f o l i a  
can be d i s t inguished  f w m  each o t h e r  and from surrounding uplands i n  
ERTS-1 scanner  bands W6 and 67. S imi la r ly ,  major impounded a r e a s ,  b u i l t  
t o  a t t r a c t  water  fowl, can be  i d e n t i f i e d .  Mosquito c o n t r o l  drainage 
d i t ches  and p l a n t  spec i e s  such as Phragmitee communis which n a t u r a l l y  
occur i n  small ,  d i spersed  patches a r e  impossible  t o  d! s c r imina t e  w i t h i n  
t he  r e so lu t i on  c a p a b i l i t y  of t he  ERTS-1 scanner.  In  d i s tu rbed  
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aarshes  of nor thern  Delaware Bay. Phragmites cornnunis does occupv l a rge  
enough expanses of marsh t o  be de tec ted .  I n  summary, i t  appears from 
prriii~lirlciry c i 1 1 ~ 1 y b L s  chat  s p e c t r a l  discrimination c a p a b i l i t i e s  of ERTS-1 
imagery compare favorably with those of a e r i a l  i n f r a r ed  photographv and 
t h a t  s p a t i a l  r e so lu t i on  is the  dominant f a c t o r  l i m i t i n g  the p o t e n t i a l  
f o r  d e t a i l e d  . legetat ion mapping using ERTS-1 irragery. 
INTRODUCTION 
Coastal  wetlands of the  type found along the  e n t i r e  East  Coast of 
t he  United S t a t e s  a r e  w e l l  s u i t e d  t o  remote s e w i n g  technique-,  par-  
t i c u l a ~ i ) ,  m u l t i s p e c t r a l  ana ly s i s .  Use of high a l t i t u d e  RE-57 and 'c'-2 
color - inf ra red  imagery i n  t he  mapping of vege ta t ion  i n  Delaware's s a l i n z  
marshes was h igh ly  succes s fu l  and i nd i ca t ed  t h a t  such mapping was pos s ib l e .  
Some oL the  c h a r a c t e r i s t l c s  which make c o a s t a l  marshes p a r t i c u l a r l y  
s u i t a b l e  f o r  m u l t i s p e c t r a l  sens ing  from high a l t i t u d e s  a r e :  
1 )  The lack  of topographic r e l i e f  e l imina tes  shadows and 
v a r i a t i o n s  i n  sun ang l e  ac ros s  t he  marsh. 
2) The r e l a t i v e l y  low d i v e r s i t y  of major p l a n t  spec i e s  
s i m p l i f i e s  photo- in te rpre ta t ion .  
3) Environmental changes gene ra l l y  take  p lace  over  l a r g e  
h o r i z o n t a l  d i s t ances  i n  t he  marsh; t he r e fo re ,  zones of 
r e l a t i v e l y  uniform vege ta t ion  a r e  u sua l l y  l a r g e  enough 
t o  be d i s c e r n i b l e  even on very high a l t i t u d e  imagery. 
4 )  Each of t he  primary spec i e s  i s  morphologically d i f f e r e n t  
enough t o  produce e a s i l y  d i sc r imina ted  r e f l ec t ance  
c h a r a c t e r i s t i c s ,  p a r t i c u l a r l y  i n  t h e  i n f r a r e d  po r t i on  of 
t h e  spectrum. 
Few n a t u r a l  s i t u a t i o n s  a f f o r d  such an opportuni ty t o  eva lua t e  t he  
optimum m u l t i s p e c t r a l  d i s c r imina t i on  c a p a b i l i t i e s  of p r e sen t  equipment 
whi le  providing u se fu l  d a t a  on p l a n t  spec i e s  d i s t r i b u t i o n  and land use 
over l a r g e  a r e a s  of t he  c o a s t a l  regime. 
GROUND TRUTH 
Data on t h e  d i s t r i h ~ t i o n  of vege ta t ion  spec i e s  and recent  
d r edge - f i l l  cons t ruc t ion  i n  Delaware's c o a s t a l  wetlands was 
co l l ec t ed  during t he  sp r ing  and summer of 1972. Reconnaissance on 
f o o t ,  i n  smal l  boa ts ,  and from low a l t i t u d e  a i r c r a f t  a ided i n  
t he  i n t e r p r e t a t i o n  of h igh  a l t i t u d e  RB-57 and 1J-2 imagery. Color and 
co lor - inf ra red  photographs ob ta ined  by these  a i r c r a f t  from an 
a l t i t u d e  of  60,000 f e e t  were analyzed by human i n t e r p r e t e r s  and by 
automated m u l t i s p e c t r a l  da t a  processing equipment. The r e s u l t s  
showed t h a t  f i v e  i nd iv idua l  spec i e s  o r  groups of assor l a t ed  
spec ies  could be c l e a r l y  d i sc r imina ted  on t he  b a s i s  of h igh  
a l t i t u d e  co lor - inf ra red  inagery.  I n  add i t i on ,  cons t ruc t i on  of 
housing, marinas, impoundments and o the r  a l t e r a t i o n s  of t he  marsh 
were c l e a r l y  d i s ce rn ib l e .  The d i s c r imina i i on  c l a s s e s  s e l e c t e d  
wore : 
1)  S a l t  marsh cord grass  (Spar t ina  a l t e r n i f  i n r a )  . 
2)  S a l t  marsh hay and s p i k e  g r a s s  (Spar t ina  pa t ens  L.ad 
D i s t i c h l i s  s p i c a t a ) .  
3) Reed g r a s s  (Phragmites communis) . 
4 )  High t i d e  bush and s e a  myr t le  (= f ru tescens  and 
Baccharis- h a l i m i f o l i a ) .  
5 )  Fresh water  impoundments b u i l t  t o  a t t r a c t  water  fowl. 
6) Dredge f i l l  cons t ruc t i on  s i n c e  t.he l a s t  r e v i s i o n  of 
t he  topographic maps. 
During August of 1972,  maps of a l l  of Delaware's 115,000 a c r e s  of 
c o a s t a l  wetlands were compiled a t  a  s c a l e  of 1:24,000. These maps show 
the  d i s t r i b u t i o n  of t he  s i x  vege t a t i on  and land use c l a s s e s  d t s c r ibed  
above (See F igure  1)  and may b e  overlayed onto USGS topographic maps of  
t he  a rea .  The percentage cover of each vege t a t i on  spec i e s  was ca l cu l a t ed  
bv t he  GEMS computer f o r  each of t he  boxed-in a r e a s  on t h e  b a s i s  of f a l s e  
co lo r  enhancement8 made u t i l i z i n g  t h e  GEMS analogue a n a l y s i s  c a p a b i l i t y  
(See Figure 2). 
patches of vegz ta t ion  a r e  not  d i s t inguished  from t h e i r  surroundings. 
The t a l l  reed g ra s s  Phragmites communis gene ra l l y  grows i n  patches 
too small  f o r  de t ec t i on  by SRTS-1 scanners  and so  i s  r a r e l y  v i s i b l e  
i n  t he  imagery. I n  t h e  i n d u s t r i a l i z e d  no r the rn  por t ion  of t he  Delaware 
Bay, d r edge - f i l l  opera t ions  appear t o  have f a c i l i t a t e d  t he  growth 
of Phragmites communis f a r  beyond i t s  usua l  l i m i t s  witti t he  r e s u l t  
t h a t  some small  marshes have become i n f e s t e d ,  o f t e n  t o  t he  exc lus ian  
of o the r  marsh p l a t s .  These marshes can be i d e n t i f i e t i  i n  ERTS-1 
imagery (See Figures  3 and 8). 
CONCLUSION 
While ERTS-1 imagery does not  appear t o  be app l i cab l e  t o  
d e t a i l e d  mapping t a s k s  i n  t i d a l  marshes due t o  r e so lu t i on  
l i m i t a t i o n s ,  i t s  usefv lness  i n  gross  mapping and inventorying 
opera t ions  i s  ev ident .  Complete i nven to r i e s  of marsh e x t e n t ,  
dominant spec i e s  d i s t r i b u t i o n ,  and human a l t e r a t i o n s  of t h e  
marsh could be performed over  l a r g e  a r e a s  i n  a  very  s h o r t  t ime,  
making i t  pos s ib l e  t o  conduct such surveys f r equen t ly  and a t  small  
expense. 
This  p ro j ec t  is  p a r t l y  funded through NSF-RANN, Grant GI-33369; 
NOAA Off ice  r f  Sea G r a n t ,  Grant No. GH-109; and NASA-ERTS-1, Contract  
No. NAS5-21837. 
-. 
, .. t % MISPILLION RIVER. DEL. I; , ' ., , , 
Figure 1 Overlay map of wetlurdr i n  the Nirpill ion Rivor area rhari- 
four typca of vegetations communitier, f rarh water impoundmontr, 
mosquito control ditching 8nd ~ r r h  l o s t  t o  dovelopo~mt. Fifteen 
such ground truth map. were prepared, coveting -st of Delawaretr 
wetlaobr , uming NASA RB-57 irmgery and multirpectral  uralymir 
techaiqwr. Note the appearance of Phramiter  coppRmir m a r  
developed 8r.u. The boxed-in 8r.u were analp-a111 
computer print-outs of the p e r c F t a g u  of lsiaor ve#etation 
rpicie. present. 
Figure 2 GEMS multispectral enhancement sf area enclosed i n  Box I2, 
Figure 1.  Dark prey - Spnrtina al ternif lora 
Light grey- Spartina patens and Dist ichl ir  rpicata 
Black - water and tqland treer. 
CORRELATION OF ERTS IMAGERY 
A s  expected, the  same c h a r a c t e r i s t i c s  of coas t a l  marshes 
which f r c i l i t a t e  mapping through the  use of a e r i a l  imagery and 
mul t i spec t ra l  ana lys i s  a l so  make poss ib le  the d iscr iminat ion  of 
marsh vegeta t ion  spec ies  and land use from space. ERTS-1 scanner 
bands 6 and 7 (. 7-. 8 microns and .8-1.1 microns) i n  images 
1024-15073 and 1079-15133 (August 16 and October 13, 1973) were used 
to iden t i fy  coas t a l  marsh areas  and t o  d i s t i ngu i sh  the  majcr 
vegetat ion types wi th in  them. (See Figure 3). Areas 
dominated by Spar t ina  a l t e r n i f l o r a  a re  c l e a r l y  d is t inguished  from 
those dominated by the o f t e n  assoc ia ted  spec ie s  - Spar t ina  patens 
and D i s t i c h l i s  s p i c a t a  (See Figures 3 and 4) .  The communities 
dominated by the  low shrubs Iva f ru tescens  and Baccharus ha l imi fo l i a  
can be d is t inguished  from adjacent  communities cf 2. patens and D. 
s p i c a t a  on one s i d e  and duue-beach o r  upland f o r e s t  regimes on 
the o ther  (See Figures 3 and 5). The p a t t e r n  t h a t  emerges i s  t h a t  
of the de t a i l ed  topographic and t i d a l  inundation c h a r a c t e r i s t i c s  of 
the marsh as seen  i n  the  ho r i zon ta l  zonation of those p l an t  spec ies  
s e n s i t i v e  t o  t h e i r  e l eva t ion  r e l a t i v e  t o  mean high t i de .  The major 
t i d a l  marsh environments and t h e i r  assoc ia ted  p l an t  communities 
may be general ly i d e n t i f i e d  as : 
1) "Low Marsh" - Areas inundated twice da i ly  f o r  
considerable periods of t i m e  by the  high t i des .  
Spar t ina  a l t e r n i f l o r a  dominates i n  t h i s  zone. 
2) "Marsh Meadow" - A t r a n s i t i o n a l  zone, s t i l l  inundated 
r egu la r ly  b u t  not  t o  as g r e a t  an ex ten t  a s  the low 
marsh. In  the  Delaware marshes t h i s  a r ea  is 
dominated by Spar t ina  pa tens  and D i s t i c h l i s  s p i c a t a  
e i t h e r  indiv idual ly  o r  together .  
3) "High Border" - A zone r a r e l y  reached except  by the  
h lghes t  t i d e s  b u t  e t i l l  requi r ing  a c e r t a i n  degree 
of e a l i n i t y  t r l e r ance  of i t s  inhabi tan te .  Thm, t h e  
name "high t i d e  bush" given t o  f ru t e scens ,  the  lw 
shrub which, along wi th  Baccharus h a l i m i f c l i a ,  dominates 
i n  t h i s  region. Beyond t h i s  zone i e  found e i t h e r  t he  
beach-dune o r  upland f o r e s t  regimes. 
FIGURE 3 
622 
. L. .-.r..".lr." 
I *,,.l...r-... 
* r r rc , i * l r -"  .I,..,. u ,*. 
I YZ A. r",..r L &I-. -,* 
, . " C . l  
I -.. * 
, t..--.*.. 
. >.-.".*- 
I r . ."  .r- c r v .  1- .,.-, I-. 
.- -x ' .C l  
?k BOMBAY HOOK, DEL. r, 
Figure 4 The largo conr~w.itiee of Spartina altarniflora and Spartina 
patam ahown in  thir map of the B d a y  Rook area, can be 
identified i n  the ERTS-1 bage  i n  Figuro 2. 
It REHOBOTH BEACH. DEL. 
Figure 5 The s tr ips  of f r u t e e c e ~  and Baccharis halimifolia,  shown 
i n  rhie map of the Rehoboth Beach area, can be identif ied i n  
i n  the ERTS-1 image i n  Figure 2. 
A l l  three regiuias &re nat aecessar i ig  always preeent but where 
any are  found :key are diecinguiehable from ezch other and from 
the non-nereh environment8 eurrounding them. It ehould be noted t h a t  
i n  a l l  casee, spec t ra l  iden t i f i ca t ion  i e  a matter of r e l a t i v e  
reflectance propertiee, one epeciee t o  another, axxi 130 ground t ru th  
i e  required. I dentif i ca t ion  of p lant  epeciee through absolute 
epectra l  character ie t ice  where no g r o u d  t ru th  i 8  available i e  
d i f f i c u l t  and unreliable due t o  atmoepheric perturbations of the 
ref lected l igh t .  Specie8 iden t i f i ca t ion  becomes qu i te  eaey, however, 
i f  the in te rp re te r  has some general knowledge of the epeciee 
die t r ibu t ion  i n  the area of in te res t .  Reconnaieeance f i e l d  work 
o r  even obeervationa made f r m  a l i g h t  plane a t  low a l t i t u d e  i e  
euf f i c ien t  i n  moat cases. Automated multiepectral  analyeis per- 
formed ming  the  General E lec t r i c  Multiepectral Data Proceeeing System 
wae found t o  be a useful  tool  i n  enhancing vegetation species and 
land use types on the bas is  of t h e i r  spec t ra l  signatures. Delays 
i n  the acquis i t ion of composite multiepectral  imagery have limited 
the application of t h i s  promising technique t o  date. 
Large f resh water impoundments b u i l t  t o  a t t r a c t  water fowl a re  
readily iden t i f i ab le  aa areas of standing wator (no U t t e r  what the 
t i d a l  atage) within the marah, ueually with s t r a i g h t ,  man-made 
boundariee (See Figure 3). Likewiee, the  e t ra igh t  boundaries and 
general lack of vegetation ident i fy  dredge-fi l l  a l t e ra t ion  of the 
mareh (See Figure 3). Multiepectral enhancament of emall portiona 
of ERTS image I.D. 1024-15073 a re  e h m  i n  Figurer 6 and 7. Note the 
c lea r  diecrimination between wetlands, uplmdo , rand and dredge-f ill. 
The major l imi ta t ion of ERTS-1 imagery i n  rumeying coasta l  marrhar 
appearr, not rurpr i r ingly ,  to be raaolution. Objectr o r  a r a u  of 
vegetation murt be of ru f f i c fan t  horizontal  extant t o  be wi thin  the  
r u o l u t i o n  capab i l i t i e s  of the EIITS-1 acuumr. Por t h i r  r a u o n ,  om11 
rca le  charac ta r i r t i c r  ouch u drainage ditching ara not  v i r i b l e  and rpprll 
Figure 6 >!ul:Lspcctral cdxmcemont ~f ERTS-1 image of Cape Henlopen 
diecriminating wetlands from uplands and sand. 
(I.D. 1024-15073). White - wetlands dark grey - uplands 
light grey - sand black - water 
Figure 7 Multispectral enhancement of ERTS-1 image of Stone Harbor, N.J., 
identifying wetlands, dredge-fill and sand. white - wetlands 
light grey - adjacent to wetlands - dredge fill 
darker grey in center of island - sand 
black - water 
N e w  J e r s e y  
\ 
Figure 8 Hewily developed reglow i n  northern 3.l.r.re. such u  he 
nrae around Delaware C i t y ,  ehw large concontratiom of P h r d t w  - - - - - - 
communio and marrhae lor t to developamt . 


Identification of marsh vegetation and coastal land use in ERTS-1 imagery

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