ERTS-1 and aircraft multispectral data collected over a North Dakota test site during July 1972, are compared to evaluate the capability of the satellite sensors to detect numbers and distribution of prairie ponds and lakes. Recognition maps using ERTS-1, MSS 7 data are generated using a level slicing technique. Surface water areas larger than two acres are recognized, but ponds in the one-to two-acre range are detected only at random. The proportion estimation technique will improve the accuracy of area determination and small pond detection

Gilmer, D. S.

Klett, A. T.

Work, E. A., Jr.

English

NASA Technical Reports Server

Paper W 12 
PRELIMINARY EVALUATION OF ERTS-1 FOR DETERMINING NUMBERS 
AND OISTRIBUTIOS OF PRAIRIE PONDS AND LAKES 
Edgar , Work, Jr.. . nvironrnental Research Institute of Michip,  Ann Arbor, Michip;  
David S. Cilmer, A. T .  Klett, Bureau of Sport Fisheries and Wikfliik, Northern Rairie 
Wildif Research Center, J a m t o w ,  North Dakota 
ERTS-1 and a i r c r a f t  multispecrral  da ta  collected over 
a North Dakota t e s t  s i t e  during July  1372, a r e  compared t o  
evaluate the  capabi l i ty  of the  s a t e l l i t e  sensors t o  de tec t  
nuabers and d i s t r ibu t ion  of p r a i r i e  ponds and lakes. Re- 
cognition maps using ERTS-1, MSS 7 da ta  a r e  generated using 
a l eve l  s l i c i n g  technique. Surface water areas la rger  than 
two acres a re  recognized, but ponds in the  one-to rvo-acre 
range a r e  detected only a t  random. The proportion estima- 
t ion  technique w i l l  improve the  accuracy of area d e t e r  
mination and small pond detection.  
Managesent of migratory watercowl is a responsibi l i ty  of the  Bureau 
of Sport Fisher ies  and Xi ldl i f  e (BSF&W) . I n  North America, t h e  p r i r u f  
breeding areas  of waterfowl are the p r a i r i e s  and parklands of t h e  north- 
e m  s t a t e s  and the p r a i r i e  prwincerr, and extend i n t o  northern Canada 
and Alaska. Nders  and d i s t r ibu t ions  of wetlands (natural  pids md 
lakes) i n  these regions are one of the principal  c r i t e r i a  wed i n  develop- 
ing an index of annual waterfowl production. The BSP&W, tbe C.rudi.n 
Wildlife Service, and various states and provinces have m d e  a m u l  
systematic breeding-ground surveys s ince  1947 (1). Aerial survey., coa- 
ducted i n  May and July, are used with air-ground correction f a c t o r s  t o  
provide indices f o r  breeding populations, habi ta t  conditions, and uater- 
fowl production. Additional region81 wetland 8utpayr a e  made periodi- 
c d l y  t o  assesc the l q : s m  o,cnlogical changee due t o  na tu ra l  md ? 
e c o a d c  cawrcll. t 
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Canadiari and U.  S. w i l d l i f e  t , io log i s t s  have suggested that  a re l i ab le  
production index could be derived, independent of the s i z e  of the breed- 
ing population, from an e s t i r a t e  of the nmber of pol~ds remaining i n  mid- 
July (2) .  The degrze of wetness, especia l ly  changes in  number of ponds, 
d-sing the Uay-July period is now determined from established a e r i a l  
t rznsectr .  Eiologists  have specda ted  that  these indices could be obtained 
more rapidly and accrlrately using airborne or spaceborne sel.sors and 
associated automatic data processing techniques. 
To invest igate  the  pc ten t i a l  of remote sensing techciques, i n  1968 
and 1970 the  E~vironm?ntal  Research I n s t i t u t e  of Michigan (ERIN, yr io r  t a  
1 January 1973, the  Willow Run 'Laboratories of The University of Michigan) 
conducted a s e r i e s  of alrborne multispectral  scanner ( S S )  data u t i l i z a -  
t ion  and processing experiments t o  determine capab i l i t i e s  fo r  e a s u r i n g  
sezsonal changes i n  vater:oul hab i ta t .  These scudies were conducted 30 
miles northwest of Ju~estovr . ,  Borth Dak5ta a t  the  Woodxorth Station,  a 
6-square-mile research area  operated by the BSFhW, Northern Prh i r i e  Wlld- 
l i f e  Research Center, Jarnestown. Biological in terpreta t ion and s i t e  co- 
otdinatioc vere provided by the BSFhW. 
The BSFhW and E2M a r e  presently involved I n  the processing end 
analysis of dara ob~a ined  by ERTS-1. Ear l i e r  work demo~stra ted the  
reliability of vater  recognition from processed a i r c r a f t  m l t i s p e c r r a l  
scanner data  (3, 4 and 5). Similar t e c h n i q u ~ s  a r e  now being dpplieti t o  
s a t e l l i t e  scanner data. Primary objectives of the  current work a re  t o  
map rind generace s t a t i s t i c s  an water bodies down t o  the  snalles: s i z e  
pands detectable a ~ d  t o  determine changes i n  veirness between spring and 
sumer using ERE-1, MSS 7 (0.8-1.1 urn) data.  Coincident a i r c r a f t  scanner 
and photographic data a r e  being used t o  in te rp re t  and cor re ia te  space- 
c r a f t  r esu l t s .  The i n i t i a l  ERTS-1 pass cver the Woodworth t e s t  s i t e  
0-curred i n  l a t e  July, which delayed u n t i l  1973 the evaluation of ~ a t e l l i t e  
data  f o r  Eetectjng seasonal c h ~ n g e  i n  wetlands. We an t ic ipa te  tha t  a 
sequence of May-July coordinated data  s e t s  w i l l  be sbtained i n  1973 vhich 
w i l l  p e r r i t  us  t o  conti;rue lnvcs t iga t io t s  of change iu seasonal wetness. 
The 1372 ZRTS and a i r c r a f t  da ta  have been processed t o  evaluate ERTS 
MSS da ta  f9,- determining n d e r s  and d i s t r ibu t ion  of p r a i r i e  ponds and 
iakes. W e  have dcmxstra ted the  feasibility of pond and lake mapping 
using concurrent a i r c r a f t  and spacecraft  da ta  and processing techniques 
derived from the previous a i r c r a f t  prograu. 
2. RECOGNITION TECHNIQCES 
Previms investigations have tes ted several  techniques i o r  mapping 
water bodier. Tkeae include; (1) pat tern  recognition using mul t ispectra l  
da ta  channels 13 the v i s i b l e  range, (2) thermal contras t  between water 
and a t e r r a ~ n  background. and (3) s ignal  l eve l  s l i c i n g  of radia t ion te- 
ceivec! i n  s s ing le  -:r?flective infrared band. Signal level s l i c i n g  is 
the  simplest method t o  implement because the zeflectance of water is 
ur,iform and lower than most other scene objects .  The method requires 
determining a s ignal  l eve l  which separates low radiance water bodies 
fr?m the other higher radiance objects i n  the scene. Investigators 
have evaluated t h i s  technique i n  near infrared regions (0.8-2.5 urn) and 
kave obtained good success i n  a l l  except the 2.0-2.5 un atmospheric 
window, where l e s se r  amounts of s o l a r  energy a r e  avai lable  f o r  scene 
illumination. 
Implementation of the  l eve l  s l i c i n g  technique i s  accomplished by 
f i r s t  generating a d i g i t a l  gray map. Frcz t h i s  p i c t o r i a l  representation 
sample. of water bodies and other known areas which exnivi t  low ref lec-  
tance values a r e  selected.  Histograms of the d i s t r ibu t ion  of ref lec tance  
l eve l s  fo r  each t r a in ing  category a r e  constructed. These d i s t r ibu t ions  
tend t o  be Gaussian, and the histogram fo r  water w i l l  be disp1a-A from 
the ref lec tance  d i s t r ibu t ions  of other objects.  It is  then necessary t o  
s e l e c t  a decision boccdary which separates surface water from a l l  other 
scene objects on the  bas i s  of t h e i r  reflectances.  
After determining the decision boundary ( i . e . , s l i c i n g  l e v e l ) ,  computer 
software is then used which generates a printed map of surface water. 
This arogram is a lso  capable of generating various s t a t i s t i c a l  sumar ies .  
However, t h i s  l a t t e r  f ea tu re  is  not discussed i n  t h i s  repor t .  
3. RESULTS 
Aircraf t  (ERIM C-47) and s a t e l l i t e  data  v z ~ e  col lec ted on 28 and 31 
July 1972 respectively.  The Woodworth Sta t ion is  located near the  nadir  
of the K2TS I L ~ G Z  se lected f o r  processing. Approximateiy ten perceui U; 
t h i s  frame, tncliiding the Woodworth s i t e  was precessed f o r  pond recogni- 
t ion .  Within the  processed areastwo physiographic regions,  the Mlssouri 
Coteau acd the  d r i f t  p la ins  of eas t -centra l  North Dakota,are represented. 
Occasional shallow ponds and lakes ~2 a paztly in tegra ted drainage system 
a r e  typ ica l  of the  d r i f t  p la ins .  Numerous but l e s s  shallow ponds and 
lakes and a non-integrated drainage a r e  c h a r a c t e r i s t i c  of the  Coteau. 
Both regions contain some of the bes t  waterfowl breeding areas  i n  North 
America. Figure 1 is a computer generated water recognit ion map of 
about th ree  percent of the  se lec ted ERTS frame. Ai rc ra f t  MSS video 
(1.0-1.4 um) showing a f l i g h t  l i n e  which t raneects  the  Woodworth Sta t ion 
is indicated. Fieh Lake is located near the center  of the  Sta t ion.  
Large p r b i r i e  lakes c lea r ly  d iscernible  from ERTS da ta  include Rouad 
(approximately 0.8 mile i n  diameter), Barneerand Chaee Lakes. Generally, 
surface water areas  l a rge r  than two acres  a r e  recdgnized. Each character  
(one d i g i t a l  sampling element) on t h i s  map represent  1.1 acres. I f  a 
one-acre pond were divided by two adjacent d i g i t a l  samp15ng elements, i t  
may o r  may not be recognized a s  a water body. Figure 2 compares water 
r e c o p i t i o n  maps of ponds and smaller lakes generated from both s a t e l l i t e  
and a i r c r a f t  da t a .  F i sh  Lake has two elongated bays which a r e  reprsduced 
accu ra t e ly  i n  t h e  ERTS image-y. However, some of t he  sho re l i ne  d e t a i l s  
of Big Lake a r e  l e s s  accu ra t e ly  descr ibed .  The elongated lake 1.2 mi les  
e a s t  of Big Lake has a r e a s  of emergent vege ta t ion  and a  chain of small  
open water a r e a s  which t r a i l  o f f  t o  t h e  southwest.  These d e t a i l e d  
f e a t u r e s ,  a l though shown i n  t he  a i r c r a f t  d a t a  a r e  no t  apparent  i n  the  
ERTS recogni t ion  map. 
Histograms of r e f l e c t a n c e  va lues  used t o  e s t a b l i s h  a  dec i s ion  
boundary s epa ra t i ng  water and o the r  f e a t u r e s  f o r  t he  s a t e l l i t e  and a i r -  
c r a f t  d a t a  a r e  shown i n  F igures  3 and 4 r e spec t i ve ly .  I n  t he  s p e c t r a i  
range under cons idera t ion  ( i . e ,  s a t e l l i t e  0 .8- i .1  um, a i r c r a f t  1.0-1.4 urn), 
both s o i l s  and water  have low r e f l e c ~ a n c e  va1uf.s. Hawever, r e f l e c t a n c e  
va lues  f o r  water  a r e  lower than those c h a r a c t e r i s t i c  of s o i l s ,  thus  t h e  
two can be accu ra t e ly  se2ara ted  (ERIM repo r t  i n  p r ep . ) .  An examination 
of t h e  s a t e l l i t e  and a i r c ~ a f t  recogni t ion  maps f o r  f a l s e  o r  omit ted r e -  
cogni t ions  i n d i c a t e s  t h a t  our dec i s ion  boundaries provide accura te  re- 
s u l t s .  Histograms of s e v e r a l  o the r  scene o b j e c t s  a r e  considered i n  t h e  
case  of t he  a i r c r a f t  d a t a  (Figure 4 ) .  During l a t e  J u l y  r e f l e c t a n c e  
l e v e l s  of some types  of marsh vegetacion a r e  s i m i l a r  t o  s o i l .  Shallow 
water  ~ h i c h  does not  completely mask r e f l e c t a n c e  from bottom s o i l  o r  
submerged marsh vege ta t ion  may i n d i c a t e  r e f l e c t a n c e  va lues  inrermediate  
between marsh v e g e t a t i c n / s o i l  and deep water.  Shallow water  and marsh 
vege t a t i on  histograms over lap  because t h e  shal low water  t ra i r . ing  a r e a s  
can be  expected t o  con t a in  some marsh vege t a t i on  and vice-veb:sa. The 
l o c a t i o n  of t he  shal low water r e f l e c t a n c e  d i s t r i b u t i o n  between deep water  
and s o i l  i n d i c a t e s  t h e  need t o  p l ace  a  dec i s ion  boundary f o r  wac-L re- 
cogn i t i on  using ERTS d a t a  (Figure 3 j  nea re r  t h e  s o i l  d i s t r i b u t i o n  than 
t h e  d i s t r i b u t i o n  for deep water .  The a h j l i t y  t o  s e l e c t  shal low water 
t r a i n i n g  a r e a s  from s a t e l l i t e  imagery is d i f f i c u l t  b e ~ a u s e  t he se  a r e a s  
tend t o  be small .  Because of t h i s  t h e  a v a i l a b i l i t y  of a i r c r a f t  imagery 
is important f o r  our  a n a l y s i s  of ERTS da t a .  
Figure 5 i s  an enlarged po r t i on  of t he  ERTS recogni t ion  map. The 
dashes (omitted from t h e  o t h e r  recognLtion maps) r ep re sen t  boundary 
elements having r e f l e c t a n c e  va lues  which f a l l  w i th in  t h e  range f o r  s o i l  
and marsh vege ta t ion .  This  cond i t i on  (boundary e f f e c t )  5s e s p e c i a l l y  
prominent i n  t he  s a t e l l i t e  recogni t ion  r e s u l t s .  Some of t he se  boundary 
elements iuay be a t t r i b u t e d  t o  marsh vege t a t i on  o r  ba r e  s o i l  margins 
surrounding t he  lakes .  The boundary elements probably a l s o  conta in  some 
water.  This  causes t he  acreage of t h e  l akes  t o  be underestimated because 
t he  boundary elements a r e  placed i n  t h e  so i l lmarsh  vege t a t i on  category.  
4. DISCUSSION 
Prel iminary r e s u l t s  demonstrate t h e  degree t o  which s u r f a c e  water  
condi t ions  can be determined u s i ~ g  ERTS MSS da ta .  General ly  i t  appears  
t h a t  ponds l a r g e r  than two a c r e s  a r e  recognized, while  water  bodies  i n  t h e  
one-to two-acre range a r e  de t ec t ed  or.1.y a t  random. Techniquos er . ls t  which 
can more r e l i a b l y  d e t e c t  smal l  ponds snd improve t h e  s i z e  e s t m z t e s  of 
l a r g e r  ones. These improvements a r e  f e l t  t o  be e s s e n t i a l  f o r  t h i s  a n a l y s i s .  
The proport ion es t imat ion  technique determines t he  p r o p o r t i o , ~  of o b j e c t s  
p resen t  w i th in  a r e s o l u t i o n  element using a m u l t i s p e c t r a l  da t a  s e t  a ~ d  an
app rop r i a t e  a l g o r i t b  (6 ) .  For example, boundary elements map be composed 
cf a mixture of water ,  marsh , ?ge t a t i on ,  and o ther  components. By 
es t imat ing  t he  propor t ion  of r a t e r  i n  t h e  boundary elements using t he  
propor t ion  technique,  t h e  accuracy cf l ake  acreage de te rmina t ion  and t he  
r e l ' 3 b i l i t y  of small  pond de t ec t i on  a r e  improved over t h e  s i g n a l  s l i c i n g  
tec t  ~ i q u e .  
Kith t h i s  a ccu ra t e  pond mapping c a p a b i l i t y  (corts is t ing of s i g n a l  l eve l  
s l i c i n g  augmented by t h e  propor t ion  e s t ima t ion  technique! seasona l  changes 
i n  su r f ace  water  can be more r e l i a b l y  determined. The most c"zr-effect ive 
method f o r  monitoring t he se  changes on a r eg iona l  b a s i s  w i l l  ve ry  l i k l p  
involve j o i n t  a i r c r a f t  and s a t e l l i t e  d a t a  c o l l e c t i o n  and t h e  use of a 
mu l t i s t age  sanpl ing  design.  
5. LITERATURE CITED 
1. Cr issey ,  W. F. ,  1957. Forecas t ing  waterfowl ha rves t s  by flyways. 
Trans. N.  Am. Wildl .  Conf. 22:256-268. 
2. Cr i ssey ,  W. F . ,  1969. P r a i r i e  po tholes  from a c o n t i n e n t a l  viewpoint.  
Pages 161-169 i n  Saskatoon Wetlands Seminar. Canadian Wildl.  Serv. 
Rep. Ser .  No. 6 ,  262 pp. 
3 .  Burge, W. G. and W. L. Brown, 1971. A study of waterfowl h a b i t a t  i n  
North Dakota u s ing  remote sens ing  tec.hniques. Willow Sun Labs.,  
I n s t .  Sc i .  TeChnol., The Univ. of Michigan, Ann Arbor, Tech. Rep. 
No. 2771-7-F, 61  pp. 
4. Nelson, H. K . ,  A.  T. K l e t t ,  and W. G. Burge, 1970. Monitoring 
migratory b i r d  h a b i t a t  by remote sens ing  methods. Trans. N .  Am. 
Wildl.  Nat. Resour. Conf. 35:73-84. 
5. Nelson, H.  F . ,  A .  T. K l e t t ,  and John E. Johnston, 1971. Appl ica t ion  
of remote sens ing  techniques f o r  app ra i s ing  changes i n  w i l d l i f e  
h a b i t a t .  Proc.  I n t .  Workshop on Ear th  Resour. Surv. Sys t .  Vol. 11, 
pages 263-288. Supt.  Doc., U.S.G.P.O. 
i 
6. Naiepka, R. F . ,  H. M. Horwitz, and N.  S. Thomson, 1971. Inves t iga-  
t i o n  of m u l t i s p e c t r a l  sensing of crops.  Willow Run Labs., I n s t .  Sc i .  
Technol., The Univ. of Michigan, Ann Arbor, Tech. Rep. No. 31550-30-T, 
80 PP- 
s 
\ '\ 
i B 
e $ 4  
m 5  
i i ,  
P 
(a) Processed ERTS Water Rccognition 
(Data of 1659 G.M.T., 31 July 1973) @ 
(b) Processed Aircraft Water Recognition from 
4500 ft (Data of 1358 G.M.T., 28 July 1972) 
1-1 1 statute mlle 
Figure 2 .  Comparison of de ta i l s  i n  ERTS-1 and aircraft  
recognition maps or ponds and iakes near woodworth, 
North Dakota. 
water 
40 
, I Decision . .
I I 
I I Boundary 
/ 8011 
DATA VALUE -9- 
Figure 3. Histograms of reflectance values for water and 
s o i l  t e s t  areas near Woodworth, North Dakota using ERTS-1 
data collected a t  1659 W, 31 July 1972. 
1 iC Deep Water 
I !I Decision 
DATA VALUE + 
Figure 4 .  Histograms of ref lectance  values of t e s t  areas near 
Woodworth, North Dakota using a i rcra f t  data co l lected  on 28 
Judy 1972 from 450C f e e t .  
W = water ----- - 
- soil/marsh vegetation - W W W W H W V W W -  - 
- W U W W U W W W W W W -  - W -  
- W W W W W W W W W b I W W W  -- 
- W W W W W W W W W W W ~ d W W -  - 
-:;u W W W W W W W W W W W W W -  -- - 
- , d W W W W W W W W H W W W W W  - W W W -  
-W--- - W W W W W W W - W k W W  W W W W W - -  
-WW--  - W W W W W W W - -  
--h'ww- - - - W W W W W W W W W W W W -  
- U W W W - -  - - - W W U d W U W W W W W W W W W W w -  --- 
- U H H W W W -  - W W W W W W W W W W W W - W W W W W -  - W W W -  
- W W W W W W W W W -  -- -WWW------  - W W W -  - W W W -  
- W W W W W W H W W  - W W -  --W- 
e 
- W W W -  
- - W W W W k W W W -  --- - W W -  
- - - W W W W W W W W W  ------ 
- W W W W W W W W -  - W M W -  -0- - 
- W W k W W W I I -  - W W W W W W W W -  --- 
- W W W W W -  - W W W W W W - - -  
---nu- W  W  W  
- W W W -  -W- 
-- -- 
- W- -- 
I 1 m i l ~ - ~  -- -- 
Figure 5 .  Example of boundary effect: aeeoclated with recognition 
maps of ponds and lakee near Woodworth, North Dakota using %TS-1 
data collected at  1659 GMT on 31 July 1972, 


Preliminary evaluation of ERTS-1 for determining numbers and distribution of prairie ponds and lakes

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