# Presentation: 723160

## LDCM Cloud Cover AssessmentJanuary 6th, 2009

- Pat Scaramuzza, SGT
- U.S. Geological Survey Center for Earth Resources Observation and Science
- Sioux Falls, SD
- * Work performed under U.S. Geological Survey contract 03CRCN0001

## Irish Data Set, now with Cloud Masks

**212 Landsat 7 L1Gs scenes**
- 5 scenes were excluded due to visible gain change artifacts.
- One scene had a gain change but no visible artifacts; it was retained.
**207 scenes with manual cloud masks**
- Manual masks were created by three operators at EDC.
- The classifications were clear, thick cloud, thin cloud, and shadow.
- Shadows were only masked where they were hard-edged and simple.
- 46 scenes have shadow masking.
- Cloud masks should be treated as having ~7% error.
- Based on 11 masks duplicated by all three operators.

**104 Training scenes, 103 Validation scenes.**
- Scenes were tagged based on scene content and ACCA performance.
- Tags included heavyclouds, cloudfree, shadows, lowsun, manyambig, falseclouds, and manyprovisionals.
- Division into training and validation sets was performed while attempting to equalize the quantity of each tag in each set, for each latitude zone.
**Irish data set and the accompanying cloud masks are available for download.**
- Courtesy of EDC.   Contact pscar@usgs.gov for instructions.

## Algorithms under review at EDC

- See5 CCA
- classification algorithm that works by minimizing the entropy of iterative classifications of the training data.
- COTS software See5/C5.0, by Rulequest.
- ACCA phase 1
- Only portion of L7 ACCA algorithm that creates a pixel mask.
- Poor classifier, but good at cloud/clear distinction.
- AT-ACCA
- Expansion of ACCA using a calculated thermal band (the AT band).
- AT band algorithm is created using numerical modelling software Cubist, by Rulequest.
- Expanded AT-ACCA will be AT-ACCA merged with g4 and Cirrus algorithms.
- g4
- Based on examination of the histograms of all bands and all two-band combinations.
- Threshold tests were developed from the histograms using iterative searches for maximum likelihood ratio.		(This minimizes type I error and maximizes the selected percentile.)
- Tests with performance less than the worst non-thermal ACCA tests were excluded.
- The threshold tests with the lowest type II error in each band or band combination were implemented.
- Creates cloud/clear/ambiguous classification based on the tally of tests passed.
- Cirrus
- Preliminary tests done with Hyperion data, but needs more study.
- Expected to be a simple threshold test on the OLI cirrus band.
- kmean
- Basic unsupervised classification algorithm.
- Results are poor, but the flexibility of the approach deserved study.

## See5 Results

| % error | # of scenes | % of scenes | cum. % |
| --- | --- | --- | --- |
| 0 - 5 | 62 | 60% | 60% |
| 5 - 10 | 24 | 23% | 83% |
| 10 - 15 | 7 | 7% | 90% |
| 15 - 20 | 3 | 3% | 93% |
| 20 - 25 | 1 | 1% | 94% |
| 25 - 30 | 0 | 0% | 94% |
| 30 - 35 | 3 | 3% | 97% |
| 35 - 40 | 1 | 1% | 98% |
| 40 - 45 | 1 | 1% | 99% |
| 45 - 50 | 0 | 0% | 99% |
| 50 - 55 | 1 | 1% | 100% |

- Scene level validation results

- Round B2 algorithm, 10/2008
- 104 Training scenes
- 	Pixels in training set:	7,998,842
- 		Non-saturated pixels:	6,560,940
- 		Saturated pixels:	1,437,902
- 103 Validation scenes
- 	Total number of validation pixels:	3,955,741,295

- Pixel level validation results

| Conf. % | Clear | Shadow | Thick | Thin | All Clouds | All Clear |
| --- | --- | --- | --- | --- | --- | --- |
| < 35% | 92.1% | 90.8% | 4.2% | 28.4% | 12.3% | 92.1% |
| 35-65% | 2.4% | 3.5% | 1.8% | 8.5% | 4.1% | 2.4% |
| > 65% | 5.5% | 5.7% | 94.0% | 63.1% | 83.6% | 5.5% |

- 	Total Pixels Correct:	89.0%
- 	Total Pixels False:	8.0%
- 	Total Ambiguous:	3.0%

## CCA Algorithms compared

|  | Total Pixels Correct | Total Pixels False | Total Pixels Ambiguous | Misclassified Clouds | Misclassified Clear |
| --- | --- | --- | --- | --- | --- |
| ACCAp1 | 78.8% | 6.0% | 15.2% | 10.4% | 3.6% |
| See5-rB2 | 89.0% | 8.0% | 3.0% | 12.3% | 5.5% |
| AT-ACCA | 74.6% | 7.4% | 18.0% | 10.3% | 5.6% |
|  |  |  |  |  |  |
| kmean | 48.0% | 7.7% | 44.3% | 19.0% | 1.3% |
| g40,8 | 69.6% | 5.4% | 25.0% | 4.5% | 5.9% |
|  |  |  |  |  |  |
| ATg40,8 | 82.3% | 8.4% | 9.3% | 11.5% | 6.6% |

## Confidence mask examples

**5,4,3 Image**

**ACCA p1**
**(translated to confidence mask)**

**See5 rB2**

**AT-ACCA**

**g4****0,8**

**Expanded AT-ACCA**

## Proposed System

- CCA #1
- Mask

- CCA #2
- Mask

- CCA #N
- Mask

- L1G Data
- (all bands,
- metadata,
- Lmask)

- Possible
- External
- Data

- L1G or Browse
- Archive

- Final CCA
- Mask

- See5-CCA

- Expanded
- AT-ACCA

- ...other CCAs?

- AT-ACCA and See-5 CCA are the only algorithms being implemented at this time.
- (Cirrus and g40,8 are being implemented as part of Expanded  AT-ACCA.)
- Temporal CCA may be added after OIVP.
- Other CCAs can still be added, within project constraints.

## Future Plans for CCA

**Shadows**
- All attempts at spectral shadow masking have failed.  Shadow masking must involve cloud geometry.
- Known methods do not comply with latency requirements.
- Shadow masking will not be implemented before launch, but is high priority for after launch.
**Cirrus**
- Preliminary study using Hyperion data suggests that cirrus can be detected with a simple threshold test on the OLI cirrus band.  (With some false positives over high altitude terrain.)
- Further study will be performed once OLI spectral characteristics are known.
**Other Classification Masks**
- Would be useful to have masks of water, snow/ice, terrain type, etc. as input to CCA.
- Not currently within scope, so unlikely to be implemented before launch.
**Intermediate Mask Merge**
- Currently testing a weighted vote methodology.
- Further study ongoing.
**Expansion of Study**
- Utilize data from Hyperion, ALI, and other satellites, converted to OLI-like bands.
- Involves creation of another set of training and validation scenes *with manual masks*.
- May not have the resources to do this, but will if possible.
**Journal Article**

## End of planned slides(after this are supporting slides)

***End of planned slides****(after this are supporting slides)*

## ACCA Phase 1 Flowchart

- Cold Cloud

- Warm Cloud

- Snow/Ice

- NDSI
- Non-Cloud

- B6 Non-Cloud

- B5 Non-Cloud

- B3 Non-Cloud
- (water)

- Ambiguous

## AT-ACCA w/g40,8 Flowchart

- AT-ACCA w/g40,8 Flowchart

- Snow/Ice

- NDSI
- Non-Cloud

- B6 Non-Cloud

- B5 Non-Cloud

- B3 Non-Cloud
- (water)

- Ambiguous

**Cloud**

- Hits < 8

- Hits = 0

- g4 Non-Cloud

- Ambiguous

- g40,8

- (Note:  No warm/cold cloud designation)

- AT-ACCA

## LDCM Cloud Mask File

- The proposed format of the final CCA mask file is 16 bit, including 4 classes and an artifact mask.
- Two-bit confidence levels:
**00** = None or Unset.
**01** = 0-35% confidence
**10** = 36-64% confidence
**11** = 65-100% confidence
- The artifact mask may contain a similar 'contribution level', marking how much of a given pixel's radiance is from a resampled artifact.
- This file format is preliminary and may change.
- Water and snow masks are currently only being developed in the AT-ACCA algorithm, and they have no confidence values.

| Bit | Description |
| --- | --- |
| 0 | Designated Fill |
| 1 | Water |
| 2 | Water Confidence |
| 3 |  |
| 4 | Snow/Ice |
| 5 | Snow/Ice Confidence |
| 6 |  |
| 7 | Cirrus |
| 8 | Cirrus Confidence |
| 9 |  |
| 10 | Cloud |
| 11 | Cloud Confidence |
| 12 |  |
| 13 | Artifact masks |
| 14 |  |
| 15 |  |

## LDCM Intermediate Cloud Mask Files

- Two-bit confidence levels:
**00** = None or Unset.
**01** = 0-35% confidence
**10** = 36-64% confidence
**11** = 65-100% confidence

| Bit | Description |
| --- | --- |
| 0 | Class |
| 1 |  |
| 2 | Class Confidence |
| 3 |  |
| 4 | Cirrus Confidence |
| 5 |  |
| 6 | Cloud Confidence |
| 7 |  |

- Two-bit class flags:
**00** = Fill
**01** = Undetermined
**10** = Water
**11** = Snow/Ice

## ACCA phase 1 Results

| % error | # of scenes | % of scenes | cum. % |
| --- | --- | --- | --- |
| 0 - 5 | 55 | 53% | 53% |
| 5 - 10 | 22 | 21% | 75% |
| 10 - 15 | 12 | 12% | 86% |
| 15 - 20 | 5 | 5% | 91% |
| 20 - 25 | 4 | 4% | 95% |
| 25 - 30 | 0 | 0% | 95% |
| 30 - 35 | 0 | 0% | 95% |
| 35 - 40 | 1 | 1% | 96% |
| 40 - 45 | 0 | 0% | 96% |
| 45 - 50 | 0 | 0% | 96% |
| 50 - 55 | 0 | 0% | 96% |
| 55 - 60 | 1 | 1% | 97% |
| 60 - 65 | 0 | 0% | 97% |
| 65 - 70 | 0 | 0% | 97% |
| 70 - 75 | 0 | 0% | 97% |
| 75 - 80 | 1 | 1% | 98% |
| 80 - 85 | 2 | 2% | 100% |
|  |  |  |  |
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- Scene level validation results

- 103 Validation scenes	 (same validation data as See5 rB2 results)
- Total number of validation pixels:	3,945,094,408

- Pixel level validation results

| Class | Clear | Shadow | Thick | Thin | All Clouds | All Clear |
| --- | --- | --- | --- | --- | --- | --- |
| Non-Cloud | 80.0% | 74.4% | 4.4% | 22.3% | 10.4% | 80.0% |
| Ambig. | 16.4% | 22.0% | 6.8% | 25.0% | 12.9% | 16.4% |
| Cloud | 3.6% | 3.6% | 88.8% | 52.6% | 76.7% | 3.6% |

- 	Total Pixels Correct:	78.8%
- 	Total Pixels False:	6.0%
- 	Total Ambiguous:	15.2%

## AT-ACCA Results

| % error | # of scenes | % of scenes | cum. % |
| --- | --- | --- | --- |
| 0 - 5 | 51 | 50% | 50% |
| 5 - 10 | 16 | 16% | 65% |
| 10 - 15 | 12 | 12% | 77% |
| 15 - 20 | 8 | 8% | 84% |
| 20 - 25 | 7 | 7% | 91% |
| 25 - 30 | 2 | 2% | 93% |
| 30 - 35 | 0 | 0% | 93% |
| 35 - 40 | 1 | 1% | 94% |
| 40 - 45 | 2 | 2% | 96% |
| 45 - 50 | 0 | 0% | 96% |
| 50 - 55 | 0 | 0% | 96% |
| 55 - 60 | 1 | 1% | 97% |
| 60 - 65 | 0 | 0% | 97% |
| 65 - 70 | 0 | 0% | 97% |
| 70 - 75 | 1 | 1% | 98% |
| 75 - 80 | 0 | 0% | 98% |
| 80 - 85 | 1 | 1% | 99% |
| 85 - 90 | 1 | 1% | 100% |
|  |  |  |  |
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- Scene level validation results

- 103 Validation scenes	 (same validation data as See5 rB2 results)
- Total number of validation pixels:	3,880,460,393

- Pixel level validation results

| Class | Clear | Shadow | Thick | Thin | All Clouds | All Clear |
| --- | --- | --- | --- | --- | --- | --- |
| Non-Cloud | 74.7% | 68.5% | 4.4% | 22.2% | 10.3% | 74.6% |
| Ambig. | 19.8% | 24.4% | 8.3% | 27.9% | 14.9% | 19.8% |
| Cloud | 5.6% | 7.1% | 87.3% | 49.9% | 74.8% | 5.6% |

- 	Total Pixels Correct:	74.6%
- 	Total Pixels False:	7.4%
- 	Total Ambiguous:	18.0%

- (This version of AT-ACCA does not distinguish between Clouds and
- Provisional clouds.)

## g40,8 Results

| % error | # of scenes | % of scenes | cum. % |
| --- | --- | --- | --- |
| 0 - 5 | 49 | 48% | 48% |
| 5 - 10 | 12 | 12% | 59% |
| 10 - 15 | 16 | 16% | 75% |
| 15 - 20 | 8 | 8% | 83% |
| 20 - 25 | 2 | 2% | 84% |
| 25 - 30 | 3 | 3% | 87% |
| 30 - 35 | 3 | 3% | 90% |
| 35 - 40 | 0 | 0% | 90% |
| 40 - 45 | 1 | 1% | 91% |
| 45 - 50 | 1 | 1% | 92% |
| 50 - 55 | 1 | 1% | 93% |
| 55 - 60 | 2 | 2% | 95% |
| 60 - 65 | 1 | 1% | 96% |
| 65 - 70 | 1 | 1% | 97% |
| 70 - 75 | 1 | 1% | 98% |
| 75 - 80 | 1 | 1% | 99% |
| 80 - 85 | 1 | 1% | 100% |
|  |  |  |  |
|  |  |  |  |
|  |  |  |  |

- Scene level validation results

- 103 Validation scenes	 (same validation data as See5 rB2 results)
- Total number of validation pixels:	3,955,741,397

- Pixel level validation results

| Class | Clear | Shadow | Thick | Thin | All Clouds | All Clear |
| --- | --- | --- | --- | --- | --- | --- |
| Non-Cloud | 71.1% | 49.1% | 1.3% | 10.7% | 4.4% | 70.9% |
| Ambig. | 23.0% | 48.6% | 23.9% | 37.0% | 28.3% | 23.2% |
| Cloud | 5.9% | 2.3% | 74.8% | 52.3% | 67.3% | 5.9% |

- 	Total Pixels Correct:	69.6%
- 	Total Pixels False:	5.4%
- 	Total Ambiguous:	25.0%

## ATg40,8 Results

| % error | # of scenes | % of scenes | cum. % |
| --- | --- | --- | --- |
| 0 - 5 | 60 | 58% | 56% |
| 5 - 10 | 17 | 17% | 75% |
| 10 - 15 | 12 | 12% | 86% |
| 15 - 20 | 5 | 5% | 91% |
| 20 - 25 | 3 | 3% | 94% |
| 25 - 30 | 1 | 1% | 95% |
| 30 - 35 | 0 | 0% | 95% |
| 35 - 40 | 1 | 1% | 96% |
| 40 - 45 | 0 | 0% | 96% |
| 45 - 50 | 0 | 0% | 96% |
| 50 - 55 | 0 | 0% | 96% |
| 55 - 60 | 1 | 1% | 97% |
| 60 - 65 | 0 | 0% | 97% |
| 65 - 70 | 1 | 1% | 98% |
| 70 - 75 | 1 | 1% | 99% |
| 75 - 80 | 1 | 1% | 100% |
|  |  |  |  |
|  |  |  |  |
|  |  |  |  |
|  |  |  |  |

- Scene level validation results

- 103 Validation scenes	 (same validation data as See5 rB2 results)
- Total number of validation pixels:	3,955,741,397

- Pixel level validation results

| Class | Clear | Shadow | Thick | Thin | All Clouds | All Clear |
| --- | --- | --- | --- | --- | --- | --- |
| Non-Cloud | 83.4% | 75.4% | 4.6% | 25.2% | 11.5% | 83.4% |
| Ambig. | 10.0% | 16.9% | 4.5% | 14.9% | 8.1% | 10.0% |
| Cloud | 6.6% | 7.8% | 90.8% | 59.9% | 80.4% | 6.6% |

- 	Total Pixels Correct:	82.3%
- 	Total Pixels False:	8.4%
- 	Total Ambiguous:	9.3%

## Comparison of all CCA algorithmsunder review at EDC

|  | Total Pixels Correct | Total Pixels False | Total Pixels Ambiguous | Misclassified Clouds | Misclassified Clear |
| --- | --- | --- | --- | --- | --- |
| See5-rB2 | 89.0% | 8.0% | 3.0% | 12.3% | 5.5% |
| ACCAp1 | 78.8% | 6.0% | 15.2% | 10.4% | 3.6% |
| AT-ACCA | 74.6% | 7.4% | 18.0% | 10.3% | 5.6% |
|  |  |  |  |  |  |
| kmean | 48.0% | 7.7% | 44.3% | 19.0% | 1.3% |
| g45 | 53.4% | 3.4% | 43.2% | 9.4% | n/a |
| g40,8 | 69.6% | 5.4% | 25.0% | 4.5% | 5.9% |
| g40,8AT | 81.5% | 9.1% | 9.4% | 8.9% | 9.3% |
| ATg40,8 | 82.3% | 8.4% | 9.3% | 11.5% | 6.6% |
| ATg40,8km | 87.7% | 10.4% | 1.9% | 16.9% | 6.7% |
| g45AT | 84.5% | 7.6% | 7.9% | 14.5% | 3.7% |
| g45kmAT | 86.4% | 11.6% | 2.0% | 28.3% | 2.1% |
| ATkm | 84.7% | 10.9% | 4.3% | 20.2% | 5.6% |

## AT equations 

- ATv4 Cubist r1 =	+ 442 * B1 	- 895 * cS * B1
- 	- 405 * B2	+ 714 * cS * B2
- 	- 147.3 * B3	+ 331 * cS * B3
- 	+ 38.3 * B4	- 141 * cS * B4
- 	- 197.1 * B5	+ 549 * cS * B5
- 	+ 430.1 * B7	- 960 * cS * B7
- 	- 15.9 * NDVI	- 17.2 * NDxI
- 	+ 5.1 * (B4/B3)	- 3.7 * (B4/B2)
- 	+ 302.2927

- where	cS	=	cos(solar elevation angle)
- 	NDVI	=	(B4-B3)/(B4+B3)
- 	NDxI	=	(B1-B7)/(B1+B7)

- All AT algorithms in this presentation use the 'ATv4 Cubist r1' formulation, as presented in the June 2008 LST.

## g4 Parameter study example --Combinations of B3 & B4

|  |  |  |  | Type I   Error | Type II   Error | Accuracy |  |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Parameter Combination | Low Threshold | High Threshold | Likelihood Ratio | Mis- classified clouds | Mis- classified clear | 1- Average Error | Percentile |
| B4/CB3 | 1.812 | 9.058 | 1.223 | 98.451% | 1.144% | 50.203% | 98.731% |
| NDC43 | -0.288 | 0.287 | 8.372 | 5.061% | 57.543% | 68.698% | 30.858% |
| ND43 | -0.064 | 0.514 | 12.550 | 2.580% | 65.000% | 66.210% | 24.944% |
| CB4/B3 | 0.480 | 1.866 | 14.534 | 2.117% | 66.286% | 65.799% | 23.913% |
| B4/B3 | 0.763 | 2.870 | 19.149 | 1.469% | 68.474% | 65.029% | 22.203% |
| B4/B3 | 1.035 |   | 0.729 | 36.778% | 72.085% | 45.569% | 29.779% |
| ND4C3 | 0.000 | 0.707 | 12.458 | 1.494% | 77.633% | 60.437% | 15.892% |
| B4/B3 |   | 2.397 | 7.310 | 2.552% | 77.854% | 59.797% | 16.068% |
|   |   |   |   |   |   |   |   |
| worst non-thermal ACCA tests |  |  | > 3.800 | < 8.100% | < 79.900% | > 60.000% | > 15.800% |

- Various combinations of B3 and B4 were examined.  A set of thresholds for each combination was derived by an iterative maximum likelihood ratio test.  The combinations were then excluded if they did not meet the criteria set by the worst non-thermal ACCA tests.  The remaining combinations were ranked by Type II error, and the best (NDC43) was implemented in the g4 decision tree.
- (Ranking by Likelihood ratio was attempted, but the results were inferior to the TII ranking method.)
- This examination was performed for 284 combinations -- including all two-band combinations, the AT band, and the ACCA-based parameter (1-B5)*AT.  A total of 22 threshold tests were implemented in this fashion.

## g40,8 Threshold Tests 

- cS*B1	< 0.101
- B2	< 0.144
- B3	< 0.140

- B5/nfac	< 0.064
- B7/nfac	< 0.048
- AT	> 301.8

- ND(B2,B1)	< -0.108	or  > 0.049
- ND(B3,B1)	< -0.192	or  > 0.029
- ND(B4,B1)	< -0.140	or  > 0.408
- ND(B1,cS*B5)	<  0.024	or  > 0.834
- ND(B1,B7)	< -0.056	or  > 0.854
- ND(B3,B2) 	< -0.096	or  > 0.046
- ND(B4,B2) 	< -0.070	or  > 0.420
- ND(B2,B5) 	< -0.160	or  > 0.801

- ND(B2,B7) 	< -0.021	or  > 0.838 ND(cS*B4,B3)	< -0.288	or  > 0.287
- ND(cS*B3,B5)	< -0.490	or  > 0.786
- ND(B3,B7)	< -0.040	or  > 0.842
- ND(cS*B4,B5) 	< -0.280	or  > 0.777
- ND(cS*B4,B7) 	< -0.200	or  > 0.819
- ND(cS*B5,B7) 	< -0.210	or  > 0.210

- (1-B5)*AT	> 262.3

- Variant g40,8 --
- If 0 tests are true, Cloud.
- If 8 or more tests are true, Clear.
- All other outcomes are ambiguous.

## p16 r29 -- Image

- Path/Row 16/29
- 5/21/2001
- 5,4,3 band
- combination

- Cloud bank
- over vegetation
- with urban areas.

- CCA Difficulty:  Easy

## p16 r29 -- Manual Mask

## p16 r29 -- See5 rB2 confidence mask

- See5 rB2 result
- 60.4% clouds
- 	1.6% ambiguous

## p16 r29 -- Expanded AT-ACCA confidence mask

- Expanded
- AT-ACCA result
- 62.0% clouds
- 	10.6% ambiguous

## p16 r29 -- ACCA phase 1 mask

- ACCA phase 1 result
- 	61.1% clouds
- 	(0.1% provisional)
- 	17.7% ambiguous

- Final ACCA result
- 60.3% clouds

## p189 r47 -- Image

- Path/Row 189/47
- 8/5/2001
- 7,4,2 band
- combination

- Thick and thin clouds
- over dark and bright
- desert.

- CCA Difficulty:  Moderate

## p189 r47 -- Manual Mask

## p189 r47 -- See5 rB2 confidence mask

- See5 rB2 result
- 	5.6% clouds
- 	1.5% ambiguous

## p189 r47 -- Expanded AT-ACCA confidence mask

- Expanded
- AT-ACCA result
- 	4.6% clouds
- 	1.6% ambiguous

## p189 r47 -- ACCA phase 1 mask

- ACCA phase 1 result
- 	4.5% clouds
- 	(0.0% provisional)
- 	7.4% ambiguous

- Final ACCA result
- 4.6% clouds

## p76 r92 -- Image

- Path/Row 76/92
- 1/17/2001
- 5,4,3 band
- combination

- Heavy cloud cover,
- with some snow.

- CCA Difficulty:  Moderate

## p76 r92 -- Manual Mask

## p76 r92 -- See5 rB2 confidence mask

- See5 rB2 result
- 	68.5% clouds
- 	1.5% ambiguous

## p76 r92 -- Expanded AT-ACCA confidence mask

- Expanded
- AT-ACCA result
- 	68.5% clouds
- 	5.5% ambiguous

## p76 r92 -- ACCA phase 1 mask

- ACCA phase 1 result
- 	67.8% clouds
- 	(1.6% provisional)
- 	9.6% ambiguous

- Final ACCA result
- 67.1% clouds

## p143 r38 -- Image

- Path/Row 143/38
- 5/31/2001
- 7,5,2 band
- combination

- Popcorn clouds
- over veg and snow.

- CCA Difficulty:  High

## p143 r38 -- Manual Mask

## p143 r38 -- See5 rB2 confidence mask

- See5 rB2 result
- 46.6% clouds
- 	5.6% ambiguous

## p143 r38 -- Expanded AT-ACCA confidence mask

- Expanded
- AT-ACCA result
- 58.6% clouds
- 	2.5% ambiguous

## p143 r38 -- ACCA phase 1 mask

- ACCA phase 1 result
- 	65.1% clouds
- 	(1.7% provisional)
- 	19.8% ambiguous

- Final ACCA result
- 80.4% clouds

## p5 r115 -- Image

- Path/Row 5/115
- 12/18/2001
- 5,4,1 band combination

- Entirely snow-covered scene.
- Some thick clouds,
- with very thin cirrus and fog
- over most of scene.

- CCA Difficulty:  'Worst case'

## p5 r115 -- Manual mask

- Manual mask operator
- painted the entire scene with
- thin clouds.

## p5 r115 -- See5 rB2 confidence mask 

- p5 r115 -- See5 rB2 confidence mask

- See5 rB2 result
- 	65.3% clouds
- 	4.4% ambiguous

## p5 r115 -- Expanded AT-ACCA confidence mask 

- p5 r115 -- Expanded AT-ACCA confidence mask

- Expanded AT-ACCA result
- 	28.5% clouds
- 	0% ambiguous

## p5 r115 -- ACCA phase 1 mask

- ACCA phase 1 result
- 	20.7% clouds
- 	(8.3% provisional)
- 	7.4% ambiguous

- Final ACCA result
- 26.5% clouds