Ф fl Ф hyperspatial thermal imaging of surface …

1
Hyperspatial Thermal Imaging of Surface Hydrothermal Features at Pilgrim Hot Springs, Alaska using a small Unmanned Aerial System (sUAS) University of Alaska Fairbanks. *Corresponding author: [email protected] Christian Haselwimmer * , Rayjan Wilson, Corey Upton, Anupma Prakash, Gwen Holdmann, and Greg Walker Acknowledgements This research is funded by the Department of Energy Geothermal Technologies Programme (CID: DE-EE0002846) and the Alaska Energy Authority Renewable Energy Fund Round III. References 1. Liss, S.A. and Motyka, R.J. (1994) Pilgrim Springs KGRA, Seward Peninsula, Alaska: Assessment of uid geochemistry. Geothermal Resources Council Transactions, Vol. 18. 2. Haselwimmer, C.E., Prakash, A., and Holdmann, G. (2011) Geothermal Exploration at Pilgrim Hot Springs, Alaska using airborne thermal infrared remote sensing. Geothermal Resources Council 35th Annual Meeting, Oct 23-26, San Diego, California. 3. Haselwimmer, C.E.,Prakash, A., and Holdmann, G., (2013) Quantifying the heat ux and outow rate of hot springs using airborne thermal imagery: case study from Pilgrim Hot Springs, Alaska, Remote Sensing of Environment, 136, 37-46, http://dx.doi.org/10.1016/j.rse.2013.04.008. 1. Overview • Very high spatial resolution (hyperspatial) thermal remote sensing from small Unmanned Aerial Systems (sUAS) has potential to contribute to mapping and monitoring of geothermal features. • sUAS deployed at Pilgrim Hot Springs, Alaska with the aim of assessing the potential and practicalities of using such a system for geothermal exploration and quantitative resource assessment. • 4 cm thermal imagery provided an unprecedented capability for mapping hot springs, seeps, and the surface ow of geothermal uids. • Heat budget model was used to estimate the hot spring heat ux and discharge rate for part of the geothermal area from the calibrated FLIR imagery, which was compared against in-situ measurements. 4. Data Preprocessing • Dif culties with photogrammetric processing approach led to use of semi-automated mosaicking with PTGui using automatic exposure adjustment. • Mosaic manually registered to high resolution airborne visible image using ArcMap. • FLIR TAU 2 is uncalibrated camera: mosaic calibrated using measured temperatures of ground targets such as hot springs and black body tarps. 5. Mapping Surface Hydrothermal Features • 4cm resolution thermal imagery provides very detailed picture of the locations and extents of hot springs and the surface outow of geothermal uids. 6. Hot Spring Heat Flux Estimation • Heat budget model used to estimate hot spring heat ux and outow rate for part of the geothermal area. Heat budget for a water body (in Watts) is expressed as: Model inputs: 1) FLIR imagery for hot waters; 2) atmospheric properties; 3) average temperature of non-geothermal surface pools. sUAS FLIR derived heat ux = 0.53 MW, lower than previous results from airborne FLIR [3] = 0.75 and 0.86 MW for 2010 and 2011 data. • Results compared against heat ux estimates derived from in-situ measurements of the ow rate (see culvert location on panel 5). • In-situ ow rate used to calculate advective heat ux (Ф adv ) through the culvert (at the measured water temp) and total hot spring heat ux (Ф geo at the hot spring temp of 81˚C) using: Ф adv/geo = (h s -h amb ) where is the mass ow rate (l/s) and h s , h amb are enthalpies of water (kJ/kg) at the spring (in this case for both the measured temp and hot spring temp) and ambient water temperatures. Total hot spring heat ux from combined sUAS/in-situ = sUAS FLIR-derived heat ux (0.53 MW) + calculated advective ux (0.42 MW) = 0.95 MW Total hot spring heat ux from in-situ only = 2.93 MW • Differences due to poor calibration of sUAS FLIR and possible underestimation of FLIR approach when compared to in-situ measurements. 7. Outcomes • sUAS acquired hyperspatial thermal imagery mapped cm-scale hot springs and seeps, and the extents of hot water with much greater detail than airborne thermal imagery. • TIR imagery shows changes in hot springs possibly related to surface hydrological conditions. • sUAS thermal imagery did not provide reliable estimates of the hot spring heat ux due to signicant errors in temperature calibration of the data: due to use of uncalibrated camera. • This work highlighted practical issues to be addressed before sUAS can compete with airborne thermal imaging such as sUAS battery life, ight planning, and use of calibrated sensors. 3. sUAS Data Collection • Aeryon Scout quadcopter equipped with FLIR TAU 2: 640 x 480 pixels covering 7.5 - 13.5 μm. • Survey own over Pilgrim Hot Springs on 24/7/2013: calm day with high cloud cover. • 100m ying height = ~4cm thermal imagery, ight lines planned around extent of hot springs and thermal features mapped from ~1.5m airborne thermal imagery (own in 2010). • ~20 mins battery life (required frequent returns to base), fully autonomous execution of survey. • Coincident collection of calibration data: hot spring + tarp temperatures, atmospheric variables. 2. Pilgrim Hot Springs, Alaska • Geothermal system located ~75km NE of Nome on Seward Peninsula. • Shallow 90ºC aquifer fed from deeper reservoirs of at least ~110-150ºC [1]. • DOE/AEA funded project to undertake resource exploration and assessment. • Airborne FLIR previously used to map hot spings and quantify heat ux and outow rate: ~4.7-7 MW th [2,3]. 0 100 200 50 Meters 0 30 60ºC Hot pools Aerial Photograph 09/10/2010 Hot springs Airborne Thermal 09/10/2010 Aerial Photograph 09/10/2010 Airborne Thermal 09/10/2010 Alaska Pilgrim Hot Springs Left: Aeryon Scout quadcopter Top left: calibration target (temperature recorded with FLIR and iButton logger). Top right: temporary weather station y = 0.0008x + 10.298 20 25 30 35 40 45 50 55 60 65 10000 20000 30000 40000 50000 60000 70000 Digital Number Temperature (ºC) Above: linear gain and offset used to calibrate the mosaicked thermal imagery to surface temperature Base image: mosaicked FLIR TAU 2 thermal imagery overlain on high resolution aerial photograph Culvert: in-situ hot spring ow rate 0 50 100 25 Meters 10 60ºC Church Calibration tarp Calibration tarp Airborne thermal (~1.5 m pixels) - 09/10/2010 sUAS thermal (~4 cm pixels) - 07/24/2013 0 10 Meters Small springs (cm scale) Seep in plunge pool Water surface lms show subtle temp difference sUAS thermal Airborne thermal 0 5 Meters Springs not seen in airborne data Hot springs not seen from sUAS data • Differences in temperature between airborne and sUAS: poor calibration of TAU 2 data? • Differences in locations of hot springs: lower water table and change in surface outow? 0 Watts 13 Above: estimated hot spring heat ux for geothermal pools (in units watts/pixel) B41B-0393 Ф total = Ф geo + Ф ppt + Ф adv + Ф evap + Ф sens + Ф rad + Ф sun + Ф sky Ф geo = heat input from geothermal uids Ф ppt = heat input from precipitation Ф adv = heat ux from advection/seepage Ф evap = heat loss from evaporation Ф sens = heat loss via sensible heat transfer Ф rad = heat loss by radiation Ф sun = heat input from solar radiation Ф sky = heat input from atmospheric radiation Ф geo Ф adv Ф ppt Ф sun Ф evap Ф sens Ф rad Ф sky

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Page 1: Ф fl Ф Hyperspatial Thermal Imaging of Surface …

Hyp

ers

patia

l Therm

al I

mag

ing

of S

urf

ace H

ydro

therm

al F

eatu

res

at

Pilg

rim H

ot

Sp

ring

s,

Ala

ska u

sing

a s

mall

Unm

anned

Aeria

l Sys

tem

(sU

AS

)

Un

ivers

ity o

f A

lask

a F

airb

an

ks.

*C

orr

esp

on

din

g a

uth

or:

ch

rist

ian

@h

ase

lwim

mer.co

.uk

Ch

risti

an

Ha

se

lwim

me

r* , R

ayja

n W

ilso

n,

Co

rey U

pto

n,

An

up

ma

Pra

ka

sh

, G

we

n H

old

ma

nn

, a

nd

Gre

g W

alk

er

Ac

kn

ow

led

ge

me

nts

Th

is r

ese

arc

h i

s fu

nd

ed

by

the D

ep

art

men

t o

f E

nerg

y G

eo

therm

al

Tech

no

log

ies

Pro

gra

mm

e (

CID

: D

E-E

E0

00

28

46

) an

d t

he A

lask

a E

nerg

y A

uth

ority

Ren

ew

ab

le E

nerg

y F

un

d R

ou

nd

III.

Re

fere

nc

es

1.

Lis

s, S

.A. and

Mo

tyka, R

.J. (1

994) P

ilgrim

Sp

ring

s K

GR

A, S

ew

ard

Penin

sula

, A

lask

a: A

ssess

ment

of fluid

geo

chem

istr

y. G

eo

therm

al R

eso

urc

es

Co

uncil

Transa

ctio

ns,

Vo

l. 18.

2.

Hase

lwim

mer, C

.E., P

rakash

, A

., a

nd

Ho

ldm

ann,

G.

(2011)

Geo

therm

al

Exp

lora

tio

n a

t P

ilgrim

Ho

t S

pring

s, A

lask

a u

sing

airb

orn

e t

herm

al

infr

are

d r

em

ote

sensi

ng

. G

eo

therm

al

Reso

urc

es

Co

uncil

35th

Annual M

eeting

, O

ct

23-2

6, S

an D

ieg

o, C

alif

orn

ia.

3.

Hase

lwim

mer, C

.E.,P

rakash

, A

., a

nd

Ho

ldm

ann,

G., (

2013)

Quantify

ing

the h

eat flux a

nd

outfl

ow

rate

of

ho

t sp

ring

s usi

ng

airb

orn

e t

herm

al

imag

ery

: case

stu

dy

fro

m P

ilgrim

Ho

t S

pring

s,

Ala

ska, R

em

ote

Sensi

ng

of

Envi

ronm

ent,

136, 37-4

6, htt

p:/

/dx.d

oi.o

rg/1

0.1

016/j.r

se.2

013.0

4.0

08.

1. O

ve

rvie

w

• Very

hig

h s

patial

reso

lutio

n (

hyp

ers

patial)

therm

al

rem

ote

sensi

ng

fro

m s

mall

Un

man

ned

Aerial

Sys

tem

s (s

UA

S) has

po

tential t

o c

ontr

ibute

to

map

pin

g a

nd

mo

nito

ring

of

geo

therm

al f

eatu

res.

• sU

AS

dep

loye

d a

t P

ilgrim

Ho

t S

pring

s, A

lask

a w

ith t

he a

im o

f ass

ess

ing

th

e p

ote

ntial

an

d

pra

cticalit

ies

of

usi

ng

su

ch a sy

stem

fo

r g

eo

therm

al

exp

lora

tio

n an

d q

uan

tita

tive

re

sou

rce

ass

ess

ment.

• 4 c

m t

herm

al

imag

ery

pro

vid

ed

an u

np

reced

ente

d c

ap

ab

ility

fo

r m

ap

pin

g h

ot

sprin

gs,

seep

s,

and

th

e s

urf

ace fl

ow

of

geo

therm

al fl

uid

s.

• H

eat

bud

get

mo

del w

as

use

d t

o e

stim

ate

the h

ot

spring

heat flux a

nd

dis

ch

arg

e r

ate

fo

r p

art

of

the g

eo

therm

al

are

a f

rom

the c

alib

rate

d F

LIR

im

ag

ery

, w

hic

h w

as

co

mp

are

d a

gain

st i

n-s

itu

measu

rem

ents

.

4.

Da

ta P

rep

roc

essin

g

• D

ifficu

ltie

s w

ith

p

ho

tog

ram

metr

ic

pro

cessin

g

ap

pro

ach

led

to

u

se

of

sem

i-au

tom

ate

d

mo

saic

kin

g w

ith

PT

Gu

i u

sin

g a

uto

matic e

xp

osu

re

ad

just

men

t.

• M

osaic

m

an

ually

re

gis

tere

d

to

hig

h

reso

luti

on

airb

orn

e v

isib

le im

ag

e u

sin

g A

rcM

ap

.

• F

LIR

TA

U

2

is

un

calib

rate

d

cam

era

: m

osaic

calib

rate

d

usin

g

measu

red

te

mp

era

ture

s o

f

gro

un

d ta

rgets

su

ch

as

ho

t sp

rin

gs

and

b

lack

bo

dy

tarp

s.

5.

Ma

pp

ing

Su

rfa

ce

Hyd

roth

erm

al F

ea

ture

s

• 4

cm

reso

lutio

n t

herm

al

imag

ery

pro

vid

es

very

deta

iled

pic

ture

of

the l

ocatio

ns

and

exte

nts

of

ho

t sp

rin

gs

an

d t

he s

urf

ace o

utfl

ow

of

geo

therm

al fl

uid

s.

6. H

ot

Sp

rin

g H

ea

t F

lux E

sti

ma

tio

n

• H

eat

bud

get

mo

del

use

d t

o e

stim

ate

ho

t sp

ring

heat flux a

nd

outfl

ow

rate

fo

r p

art

of

the

geo

therm

al a

rea.

Heat

bud

get

for

a w

ate

r b

od

y (in

Watt

s) is

exp

ress

ed

as:

• M

od

el

inp

uts

: 1

) F

LIR

im

ag

ery

fo

r h

ot

wate

rs;

2)

atm

osp

heri

c

pro

pert

ies;

3) ave

rag

e t

em

pera

ture

of

no

n-g

eo

therm

al s

urf

ace p

oo

ls.

• sU

AS

FL

IR d

eri

ve

d h

ea

t fl

ux =

0.5

3 M

W,

low

er

than p

revi

ous

resu

lts

fro

m a

irb

orn

e F

LIR

[3] =

0.7

5 a

nd

0.8

6 M

W f

or

2010 a

nd

2011 d

ata

.

• R

esu

lts

co

mp

are

d ag

ain

st

heat flu

x esti

mate

s d

eri

ved

fr

om

in

-sit

u

me

asu

rem

en

ts o

f th

e fl

ow

ra

te (se

e c

ulv

ert

locatio

n o

n p

anel 5

).

• In

-situ fl

ow

rate

use

d t

o c

alc

ula

te a

dve

cti

ve

he

at fl

ux (Ф

adv)

thro

ug

h

the c

ulv

ert

(at

the m

easu

red

wate

r te

mp

) and

to

tal

ho

t sp

rin

g h

ea

t fl

ux

( Фge

o at

the h

ot

spring

tem

p o

f 81˚C

) usi

ng

:

Фad

v/ge

o = ṁ

(hs-h

amb)

w

here

ṁ is

th

e m

ass

flo

w r

ate

(l/s)

an

d h

s, h a

mb

are

en

thalp

ies

of

wate

r (k

J/k

g)

at

the s

prin

g (

in

this

case

fo

r b

oth

th

e m

easu

red

tem

p a

nd

ho

t sp

rin

g t

em

p) an

d a

mb

ien

t w

ate

r te

mp

era

ture

s.

• To

tal

ho

t sp

rin

g h

ea

t fl

ux f

rom

co

mb

ine

d s

UA

S/i

n-s

itu

= s

UA

S F

LIR

-derive

d h

eat flu

x (

0.5

3

MW

) +

calc

ula

ted

ad

vective

flux (0.4

2 M

W) =

0.9

5 M

W

• To

tal h

ot

sp

rin

g h

ea

t fl

ux f

rom

in

-sit

u o

nly

= 2

.93 M

W

• D

iffe

ren

ces

du

e to

p

oo

r calib

ratio

n o

f sU

AS

F

LIR

an

d p

ossib

le u

nd

ere

stim

atio

n

of

FL

IR

ap

pro

ach w

hen c

om

pare

d t

o in

-situ m

easu

rem

ents

.

7. O

utc

om

es

• sU

AS

acq

uired

hyp

ers

patial th

erm

al im

ag

ery

map

ped

cm

-scale

ho

t sp

ring

s and

seep

s, a

nd

th

e

exte

nts

of

ho

t w

ate

r w

ith m

uch g

reate

r d

eta

il th

an a

irb

orn

e t

herm

al i

mag

ery

.

• T

IR im

ag

ery

sho

ws

chang

es

in h

ot

spring

s p

oss

ibly

rela

ted

to

surf

ace h

ydro

log

ical c

on

ditio

ns.

• sU

AS

therm

al

imag

ery

did

no

t p

rovi

de r

elia

ble

est

imate

s o

f th

e h

ot

spring

heat flu

x d

ue t

o

sig

nifi

cant

err

ors

in t

em

pera

ture

calib

ratio

n o

f th

e d

ata

: d

ue t

o u

se o

f uncalib

rate

d c

am

era

.

• T

his

wo

rk h

ighlig

hte

d p

ractical is

sues

to b

e a

dd

ress

ed

befo

re s

UA

S c

an c

om

pete

with

airb

orn

e

therm

al i

mag

ing

such a

s sU

AS

batt

ery

life

, flig

ht

pla

nnin

g,

and

use

of

calib

rate

d s

enso

rs.

3. sU

AS

Da

ta C

olle

cti

on

• A

ery

on

Sco

ut

quad

co

pte

r eq

uip

ped

with F

LIR

TA

U 2

: 640 x

480 p

ixels

co

verin

g 7

.5 -

13

.5 μ

m.

• S

urv

ey flo

wn o

ver

Pilg

rim

Ho

t S

pring

s o

n 2

4/7

/2013:

calm

day

with h

igh

clo

ud

co

ver.

• 10

0m

flyi

ng

heig

ht

= ~

4cm

therm

al i

mag

ery

, flig

ht

lines

pla

nned

aro

und

exte

nt

of

ho

t sp

rin

gs

an

d

therm

al f

eatu

res

map

ped

fro

m ~

1.5

m a

irb

orn

e t

herm

al i

mag

ery

(flo

wn

in 2

01

0).

• ~

20 m

ins

batt

ery

life

(re

quired

fre

quent

retu

rns

to b

ase

), f

ully

auto

no

mo

us

execu

tio

n o

f su

rvey.

• C

oin

cid

en

t co

llectio

n o

f calib

ratio

n d

ata

: ho

t sp

ring

+ t

arp

tem

pera

ture

s, a

tmo

sph

eric v

ariab

les.

2.

Pilg

rim

Ho

t S

pri

ng

s,

Ala

sk

a

• G

eo

therm

al

syst

em

lo

cate

d ~

75

km

NE

of

No

me o

n S

ew

ard

Pen

insu

la.

• S

hallo

w 9

0ºC

aq

uifer

fed

fro

m d

eep

er

rese

rvo

irs

of

at

least

~1

10

-15

0ºC

[1

].

• D

OE

/AE

A f

un

ded

pro

ject

to u

nd

ert

ake

reso

urc

e e

xp

lora

tio

n a

nd

ass

ess

men

t.

• A

irb

orn

e F

LIR

pre

vio

usl

y u

sed

to

map

ho

t sp

ing

s an

d q

uan

tify

heat flu

x a

nd

outfl

ow

rate

: ~

4.7

-7 M

Wth

[2

,3].

01

00

20

05

0M

ete

rs0

30

60

ºC

Ho

t p

oo

ls

Aerial P

ho

tog

rap

h09/1

0/2

010

Ho

t sp

ring

s

Airb

orn

e T

herm

al

09/1

0/2

010

Aerial P

ho

tog

rap

h09/1

0/2

010

Airb

orn

e T

herm

al

09/1

0/2

010

Ala

sk

a

Pilg

rim

Ho

tS

pri

ngs

Le

ft: A

ery

on S

co

ut

quad

co

pte

r

Top

le

ft:

calib

ratio

n t

arg

et

(tem

pera

ture

reco

rded

with F

LIR

and

iButt

on lo

gg

er)

. To

p r

igh

t: t

em

po

rary

weath

er

statio

n

y =

0.0

00

8x +

10

.29

8

20

25

30

35

40

45

50

55

60

65 1

00

00

200

00

30

00

04

00

00

500

00

600

00

70

00

0

Dig

ital N

um

ber

Temperature (ºC)

Ab

ove

: lin

ear

gain

and

off

set

use

d t

o c

alib

rate

the

mo

saic

ked

therm

al i

mag

ery

to

surf

ace t

em

pera

ture

Ba

se

im

ag

e: m

osa

icked

FLIR

TA

U 2

therm

al i

mag

ery

o

verlain

on h

igh r

eso

lutio

n a

erial p

ho

tog

rap

h

Culv

ert

: in

-situ h

ot

spring

flo

w r

ate

05

01

00

25

Mete

rs

10

60

ºC

Churc

h

Calib

ratio

n t

arp

Calib

ratio

n t

arp

Airb

orn

e t

herm

al (

~1.5

m p

ixels

) -

09/1

0/2

010

sUA

S t

herm

al (

~4 c

m p

ixels

) -

07/2

4/2

013

010

Mete

rs

Sm

all

sprin

gs

(cm

scale

)

Seep

in

plu

ng

e p

oo

l

Wate

r su

rface fi

lms

sho

w

sub

tle t

em

p d

iffere

nce

sUA

S t

herm

al

Airb

orn

e t

herm

al

05

Mete

rs

Sp

ring

s no

t se

en

in a

irb

orn

e d

ata

Ho

t sp

ring

s no

t se

en

fro

m s

UA

S d

ata

• D

iffere

nces

in

tem

pera

ture

b

etw

een a

irb

orn

e

and

sU

AS

: p

oo

r calib

ratio

n o

f TA

U

2 d

ata

?

• D

iffere

nces

in

locatio

ns

of

ho

t sp

ring

s: lo

wer

wate

r ta

ble

and

chang

e in

surf

ace

outfl

ow

?

0W

att

s1

3

Ab

ove

: est

imate

d h

ot

spring

heat flux f

or

geo

therm

al

po

ols

(in

units

watt

s/p

ixel)

B4

1B

-03

93

Фto

tal =

Фge

o + Ф

ppt +

Фad

v + Ф

evap

+ Ф

sens

+ Ф

rad + Ф

sun

+ Ф

sky

Фge

o =

heat

inp

ut

fro

m g

eo

therm

al fl

uid

s

Фpp

t =

heat

inp

ut

fro

m p

recip

itatio

n

Фad

v =

heat flu

x f

rom

ad

vectio

n/s

eep

ag

e

Фev

ap

= h

eat

loss f

rom

evap

ora

tio

n

Фse

ns

= h

eat

loss v

ia s

en

sib

le h

eat

tran

sfe

r

Фra

d =

heat

loss b

y r

ad

iatio

n

Фsu

n =

heat

inp

ut

fro

m s

ola

r ra

dia

tio

n

Фsk

y =

h

eat

inp

ut

fro

m a

tmo

sp

heric r

ad

iatio

geo

Фad

v

Фpp

sunФ

evapФ

sens

Фra

sky