# Intercomparison and Validation of SAR-Based Ice Velocity Measurement Techniques within the Greenland Ice Sheet CCI Project

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## Abstract

**:**

## 1. Introduction

## 2. Methods

#### 2.1. Sythetic Aperture Radar Ice-Motion Measurement Techniques

#### 2.2. Experiment Description

#### 2.3. Validation Strategy

_{e}, v

_{n}, v

_{u}), with the LoS and azimuth velocity components provided by the SAR-based methods, the GPS velocities were projected onto the LoS and azimuth directions according to the following transformation:

_{r}represents the SAR LoS velocity component (positive for motion towards the radar), v

_{a}the SAR azimuth velocity component (positive for motion in the satellite flight path direction), φ the angle between the East direction and the ground projection of the SAR LoS vector, and θ the elevation angle from the horizontal plane to the SAR LoS vector. The values of these angles at scene center are listed in Table 1.

## 3. Results

#### 3.1. Differential Synthetic Aperture Radar Interferometry (Task 1)

#### 3.1.1. Measurements

#### 3.1.2. Intercomparison

#### 3.1.3. Validation

#### 3.2. Multi Aperture Interferometry (Task 2)

#### 3.2.1. Measurements

#### 3.2.2. Intercomparison

#### 3.2.3. Validation

#### 3.3. Incoherent Offset-Tracking (Task 3)

#### 3.3.1. Measurements

#### 3.3.2. Intercomparison

#### 3.3.3. Validation

#### 3.4. Partially-Coherent Offset-Tracking (Task 4)

#### 3.4.1. Measurements

#### 3.4.2. Intercomparison

#### 3.4.3. Validation

## 4. Discussion

#### 4.1. Differential Synthetic Aperture Radar Interferometry

#### 4.2. Multi Aperture Interferometry

#### 4.3. Offset Tracking

## 5. Conclusions

## Supplementary Materials

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 1.**(

**a**) SAR data frames (rectangles) and GPS stations/stakes used for validation (triangles) plotted on a horizontal velocity magnitude mosaic generated from Sentinel-1a/b SAR data acquired between October 2015 and October 2016 (©ENVEO). Insets represent the Storstrømmen (

**b**); Upernavik (

**c**) and central west ice margin (

**d**) test sites referred to in Table 1.

**Figure 2.**Interferometric coherence of the I1 (

**a**); I2 (

**b**); I3 (

**c**) and I4 (

**d**) SAR datasets (Table 1).

**Figure 3.**Task 1 LoS velocity maps provided by groups 1 to 6 (

**a**–

**f**). Positive values correspond to motion towards the radar along the LoS vector (from ground to satellite), the ground projection of which at scene center is shown by the arrow in (

**a**). Triangles represent the GPS stations used for validation.

**Figure 4.**Task 1 quality parameters provided by groups 1 to 6 (

**a**–

**f**). For group 2 (

**b**) the quality parameter is interferometric coherence, whereas for all other groups it is the predicted LoS velocity error standard deviation in m/y. Triangles represent the GPS stations used for validation. Crosses represent GCPs used for orbital refinement and absolute phase estimation.

**Figure 6.**Task 2 azimuth velocity maps provided by groups 1 to 4 (

**a**–

**d**). Positive values correspond to motion along the satellite flight path, the ground projection of which is shown with an arrow in (

**a**). The triangles represent the GPS stations used for validation.

**Figure 7.**Task 2 azimuth quality parameters provided by groups 2 (

**a**); 3 (

**b**); and 4 (

**c**). For all groups the quality parameter is the predicted azimuth velocity error standard deviation in m/y. Triangles represent the GPS stations used for validation.

**Figure 9.**Task 3 LoS velocity maps provided by groups 1 to 6 (

**a**–

**f**). Positive values correspond to motion towards the radar along the LoS vector (from ground to satellite), the ground projection of which at scene center is shown by the arrow in (

**a**). The insets correspond to the area in the dashed rectangle and show the GPS stations used for validation.

**Figure 10.**Task 3 azimuth velocity maps provided by groups 1 to 6 (

**a**–

**f**). Positive values correspond to motion along the satellite flight path, the ground projection of which is shown with an arrow in (

**a**).

**Figure 11.**Task 3 quality parameters. Groups 1 slant-range (

**a**) and azimuth error standard deviation (

**b**); group 3 NCC amplitude (

**c**); group 4 cross-correlation SNR (

**d**); group 5 NCC amplitude (

**e**); and group 6 slant-range (

**f**) and azimuth error standard deviation (

**g**). Triangles represent the GPS stations used for validation. Crosses represent GCPs used for calibration.

**Figure 12.**Task 3 LoS velocity differences of groups 1 to 5 (

**a**–

**e**) with respect to group 6. The dashed line in the inset represent the trace of the profiles shown in Figure 14.

**Figure 15.**Task 4 LoS velocity maps provided by groups 1 to 8 (

**a**–

**h**). Positive values correspond to motion towards the radar along the LoS vector (from ground to satellite), the ground projection of which at scene center is shown by the arrow in (

**a**). The insets show the GPS stations used for validation.

**Figure 16.**Task 4 azimuth velocity maps provided by groups 1 to 8 (

**a**–

**h**). Positive values correspond to motion along the satellite flight path, the ground projection of which is shown by the arrow in (

**a**).

**Figure 17.**Task 4 quality parameters. Groups 1 slant-range (

**a**) and azimuth error standard deviation (

**b**); group 4 cross-correlation signal to noise ratio (

**c**); group 5 normalized cross-correlation amplitude (

**d**); group 6 slant-range (

**e**) and azimuth error standard deviation (

**f**); group 8 slant-range (

**g**) and azimuth error standard deviation (

**h**). Triangles represent the GPS stations used for validation. Crosses represent GCPs used for velocity calibration.

**Figure 18.**Task 4 LoS velocity differences between groups 1 to 7 (

**a**–

**g**) with respect to group 8 in the area of GPS stations STO4 and AVA1. The dashed lines represent the traces of the profiles in Figure 24a,c.

**Figure 19.**Task 4 LoS velocity differences between groups 1 to 7 (

**a**–

**g**) with respect to group 8 in the area of RNK2 GPS station. The dashed lines represent the trace of the profiles in Figure 24e.

**Figure 20.**Task 4 wrapped LoS velocity maps provided by groups 1 to 8 (

**a**–

**h**) in the area of GPS stations STO4 and AVA1. Each color cycle represents a 200 m/y variation. Velocities are referred to the star (zero velocity).

**Figure 21.**Task 4 azimuth velocity differences between groups 1 to 7 (

**a**–

**g**) and group 8 in the area of GPS stations STO4 and AVA1. The dashed lines represent the traces of the profiles in Figure 24b,d.

**Figure 22.**Task 4 azimuth velocity differences between groups 1 to 7 (

**a**–

**g**) and group 8 in the area of RNK2 GPS station. The dashed line represents the trace of the profiles in Figure 24f.

**Figure 23.**Task 4 wrapped azimuth velocity maps provided by groups 1 to 8 (

**a**–

**h**) in the area of GPS stations STO4 and AVA1. Each color cycle represents a 200 m/y variation. Velocities are referred to the star (zero velocity).

**Table 1.**SAR data overview. Locations are shown in Figure 1.

Id | Location | Sensor | Acquisition | Bt ^{a} | Bp ^{b} | Df ^{c} | Θ ^{d} | Φ ^{e} | ∆r ^{f} | ∆a ^{g} |
---|---|---|---|---|---|---|---|---|---|---|

Date | (Days) | (m) | (Hz) | (°) | (°) | (m) | (m) | |||

I1 | Storstrømmen | ERS-1 | 1996-01-31 | 1 | 140 | 0 | 67 | −151 | 7.90 | 3.94 |

ERS-2 | 1996-02-01 | |||||||||

I2 | Storstrømmen | ERS-1 | 1996-04-10 | 1 | −20 | 245 | 67 | −151 | 7.90 | 3.94 |

ERS-2 | 1996-04-11 | |||||||||

I3 | Upernavik | ASAR | 2010-07-11 | 35 | 306 | −46 | 67 | −158 | 7.80 | 4.01 |

(ENVISAT) | 2010-08-19 | |||||||||

I4 | Central west | PALSAR | 2009-11-20 | 46 | 583 | 61 | 52 | −166 | 4.68 | 3.14 |

ice margin | (ALOS-1) | 2010-01-05 |

^{a}Temporal baseline;

^{b}Perpendicular baseline at scene center;

^{c}Doppler centroid difference at scene center;

^{d,e}Elevation and orientation angles at scene center in Equation (1);

^{f,g}Slant-range and azimuth pixel spacing. Acronyms: European Remote Sensing satellites 1 and 2 (ERS-1,2), Advanced Synthetic Aperture Radar (ASAR), Environmental Satellite (ENVISAT), Phased Array L-band Synthetic Aperture Radar (PALSAR), Advanced Land Observing Satellite 1 (ALOS-1).

Task | SAR Datasets | Processing Level | Auxiliary Data | Processing Algorithm | Deliverables |
---|---|---|---|---|---|

1 | I1 and I2 | SLC | DEM ^{a}, Precise SVs ^{b} | DInSAR | LoS velocity map, quality parameters, GCPs |

2 | I2 | RAW | DEM ^{a}, Precise SVs ^{b} | MAI | Azimuth velocity map, quality parameters, GCPs |

3 | I3 | RAW | DEM ^{a}, Precise SVs ^{c} | Offset Tracking | LoS and azimuth velocity maps, quality parameters, GCPs |

4 | I4 | RAW | DEM ^{a} | Offset Tracking | LoS and azimuth velocity maps, quality parameters, GCPs |

^{a}90 m posting DEM of Greenland (Byrd Polar Research Center, Ohio State University);

^{b}Precise State Vectors from Delft University of Technology;

^{c}DORIS Precise State Vectors. Acronyms: Single Look Complex (SLC), Differential Synthetic Aperture Radar Interferometry (DInSAR), Multi Aperture Interferometry (MAI), Ground Control Points (GCPs).

Group | G1 | G2 | G3 | G4 | G5 | G6 |
---|---|---|---|---|---|---|

Method | DEME | DEME | DEME | DD | DEME | DD |

Quality parameter ^{a} | σ | γ | σ | σ | σ | σ |

Coregistration ^{b} | N_{w}: 20 × 20,W _{s}: 64 × 256,N _{poly}: 2 | N_{w}: 64 × 128, W _{s}: 64 × 64,N _{poly}: 2. | N_{w}: 20 × 20,W _{s}: 64 × 256,N _{poly}: 2 | N_{w}: 8 × 16,W _{s}: 128 × 128,N _{poly}: 0 | N_{w}: 8 × 16,W _{s}: 128 × 128,N _{poly}: 0 | N_{w}: 20 × 20,W _{s}: 64 × 256,N _{poly}: 2 |

Interferogram filtering ^{c} | N_{L}: 2 × 10, Goldstein(N _{fft}: 32, α: 0.5) | N_{L}: 2 × 10, Goldstein(N _{fft}: 32, α: 0.8) | N_{L}: 2 × 10, Goldstein(N _{fft}: 32, α: 0.5) | N_{L}: 3 × 15 | N_{L}: 3 × 15 | N_{L}: 2 × 10, Goldstein(N _{fft}: 32, α: 0.5) |

Phase unwrapping ^{d} | Branch cut (γ _{thr} = 0.41) | MCF (γ _{thr} = 0.3) | MCF (γ _{thr} = 0.41) | MCF (γ _{thr} = 0.3) | MCF (γ _{thr} = 0.3) | MCF (γ _{thr} = 0.41) |

Geophysical inversion | 49 GCPs | 1 GCP | 20 GCPs | 20 GCPs | 20 GCPs | 20 GCPs |

Geocoding ^{e} | EQA, 280 m × 250 m | PS, 45 m × 45 m | EQA, 45 m × 45 m | EQA, 45 m × 45 m | EQA, 45 m × 45 m | EQA, 45 m × 45 m |

^{a}σ: per-pixel error standard deviation (m/y), γ: interferometric phase coherence;

^{b}N

_{w}: number of cross-correlation windows (range × azimuth), W

_{s}: cross-correlation window size (range × azimuth), N

_{poly}: polynomial degree for co-registration refinement;

^{c}N

_{L}: number of interferogram looks (range × azimuth), N

_{fft}: Goldstein filter 2D FFT size and α parameter [27];

^{d}γ

_{thr}: coherence threshold;

^{e}EQA: lat/lon grid, PS: NSIDC Polar Stereographic North (EPSG 3413). Acronyms: Digital Elevation Model Elimination (DEME), Double Difference (DD). Minimum Cost Flow (MCF). Ground Control Points (GCPs), Equal Area (EQA), Polar Stereographic (PS).

Parameter | Component | Group | |||||
---|---|---|---|---|---|---|---|

G1 | G2 | G3 | G4 | G5 | G6 | ||

SAR–GPS | |||||||

N ^{a} | LoS | 10 | 10 | 10 | 10 | 10 | 10 |

Median ^{b} | LoS | 40.48 | −0.71 | 1.13 | 0.55 | 1.07 | 0.93 |

MAD ^{c} | LoS | 13.70 | 0.55 | 0.58 | 0.59 | 0.58 | 0.81 |

Bedrock | |||||||

Median | LoS | 3.1 | −1.41 | 0.36 | −0.21 | 0.24 | 0.30 |

MAD | LoS | 29.7 | 0.99 | 0.82 | 0.74 | 0.89 | 0.71 |

^{a}Number of co-located SAR and GPS measurements;

^{b}Median of SAR differences with respect to GPS in m/y;

^{c}Median Absolute Deviation (MAD) of SAR differences with respect to GPS in m/y.

Group | G1 | G2 | G3 | G4 |
---|---|---|---|---|

Quality parameter ^{a} | - | σ | σ | σ |

Sub-aperture formation ^{b} | n: 0.4 | n: 0.4 | n: 0.4 | n: 0.5 |

Interferogram filtering ^{c} | N_{L}: 4 × 20,Goldstein (N _{fft}: 64, α: 0.8) | N_{L}: 4 × 20,Mean filter (12 pixel radius) | N_{L}: 4 × 20,Mean filter (18 pixel radius) | N_{L}: 4 × 20,Goldstein (N _{fft}: 64, α: 0.5),Ionospheric filter |

Phase unwrapping ^{d} | - | - | - | MCF |

Geophysical inversion | Δ_{f}, V_{g} scaling | Δ_{f}, V_{g} scaling | Δ_{f}, V_{g} scaling | Orbital refinement, L _{a} scaling |

Geocoding ^{e} | PS, 90 m × 90 m | EQA, 90 m × 90 m | EQA, 90 m × 90 m | PS, 90 m × 90 m |

^{a}σ: per-pixel error standard deviation (m/y);

^{b}n: normalized Doppler frequency separation between sub-apertures (as a fraction of the 1680 Hz PRF);

^{c}N

_{L}: number of interferogram looks (range × azimuth), N

_{fft}: Goldstein filter 2D FFT size, and α parameter [27], r: mean filter radius in pixels;

^{d}L

_{a}: nominal antenna length, Δf: sub-aperture frequency separation, V

_{g}: ground (beam footprint) velocity;

^{e}EQA: lat/lon grid, PS: NSIDC Polar Stereographic North (EPSG 3413).

Parameter | Component | Group | |||
---|---|---|---|---|---|

G1 | G2 | G3 | G4 | ||

SAR–GPS | |||||

N ^{a} | Azimuth | 9 | 10 | 10 | 10 |

Median ^{b} | Azimuth | 4.97 | 11.6 | 4.78 | 3.58 |

MAD ^{c} | Azimuth | 10.35 | 17.99 | 13.59 | 6.80 |

Bedrock | |||||

Median | Azimuth | 6.83 | −3.82 | −3.24 | 0.12 |

MAD | Azimuth | 12.89 | 19.46 | 17.08 | 3.39 |

^{a}Number of co-located SAR and GPS measurements;

^{b}Median of SAR differences with respect to GPS in m/y;

^{c}Median Absolute Deviation (MAD) of SAR differences with respect to GPS in m/y.

Group | G1 | G2 | G3 | G4 | G5 | G6 |
---|---|---|---|---|---|---|

Method ^{a} | ICC | ICC | ICC | ICC | ICC | ICC |

Quality parameter ^{b} | σ | - | NCC | SNR | NCC | σ |

Pre-processing | Coregistration | 1 × 5 multi-look; High-pass | Coregistration | Coregistration | - | - |

Offset computation ^{c} | Osf: 2, W _{s}: 1300 × 1000,W _{p}: 200 × 200 | Osf: 2, W _{s}: 1600 × 1600,W _{p}: 100 × 100,S _{s}: 2300 × 2300 | Osf: 16, W _{s}: 650 × 256,W _{p}: 100 × 100 | Osf: 2, W _{s}: 1300 × 1000,W _{p}: 240 × 200 | Osf: 8 W _{s}: 2000 × 400,W _{p}: 400 × 200,S _{s}: 650 × 130 | Osf: 2, W _{s}: 1300 × 1000,W _{p}: 200 × 200 |

Outlier ulling ^{d} | SNR_{thr} = 7.0,Max. velocity | SNR_{thr} = 2.5,Max. velocity, Local variability (magnitude and direction) | NCC_{thr} = 0.15,Local variance | SNR_{thr} = 4.0,Unclear | NCC_{thr} = 0.05 | SNR_{thr} = 7.0,NCC _{thr} = 0.05 |

Filtering | Moving average (5 × 5 window) | - | Anisotropic diffusion | - | - | Moving average (5 × 5 window) |

Geophysical inversion | Stationary GCPs | - | - | High-SNR GCPs | - | Stationary GCPs |

Geocoding ^{e} | EQA, 280 m × 250 m | PS, 100 m × 100 m | PS, 100 m × 100 m | PS, 90 m × 90 m | PS, 90 m × 90 m | PS, 250 m × 250 m |

^{a}ICC: Intensity cross-correlation;

^{b}σ: per-pixel error standard deviation (m/y), NCC: normalized cross-correlation, SNR: cross-correlation peak Signal to Noise Ratio;

^{c}Osf: oversampling factor, W

_{s}, W

_{p}: cross-correlation window size and spacing in m (ground range × azimuth), S

_{s}: search window size in m (ground range × azimuth);

^{d}SNR

_{thr}: SNR threshold, NCC

_{thr}: NCC threshold;

^{e}EQA: lat/lon grid, PS: NSIDC Polar Stereographic North (EPSG 3413).

Parameter | Component | Group | |||||
---|---|---|---|---|---|---|---|

G1 | G2 | G3 | G4 | G5 | G6 | ||

SAR–GPS | |||||||

N ^{a} | LoS | 7 | 4 | 3 | 4 | 8 | 6 |

Azimuth | 7 | 4 | 3 | 4 | 10 | 6 | |

Median ^{b} | LoS | −12.3 | −16 | −5.45 | −15.8 | −15.6 | 1.01 |

Azimuth | −34.9 | −11.4 | −67.0 | 4.72 | 12.3 | −14.1 | |

MAD ^{c} | LoS | 27.6 | 23.5 | 21.1 | 50.5 | 1450 | 21.2 |

Azimuth | 52.3 | 56.1 | 70.0 | 90.9 | 772 | 42.6 | |

Bedrock | |||||||

Median ^{b} | LoS | −1.10 | 0.40 | −2.20 | 1.10 | 10.2 | 0.60 |

Azimuth | 0.20 | −39.3 | −8.10 | −1.50 | 5.20 | 0.0 | |

MAD ^{c} | LoS | 2.43 | 6.74 | 5.13 | 4.92 | 3.26 | 2.16 |

Azimuth | 1.15 | 29.95 | 5.67 | 9.24 | 10.5 | 1.82 |

^{a}Number of co-located SAR and GPS measurements;

^{b}Median of SAR-GPS differences in m/y;

^{c}Median absolute deviation of SAR differences with respect to GPS in m/y.

Group | G1 | G2 | G3 | G4 | G5 | G6 | G7 | G8 |
---|---|---|---|---|---|---|---|---|

Method ^{a} | ICC | ICC | ACC | ICC | ICC | ICC | CCC and ACC | ICC |

Quality parameter ^{b} | σ | - | - | SNR | NCC | σ | σ | σ |

Pre-processing | Coregistration | 1 × 2 multi-look, High-pass filter | - | Coregistration | - | Coregistration | Coarse ACC Interf. formation | - |

Offset computation ^{c} | Osf: 2, W _{s}: 960 × 800,W _{p}: 150 × 150 | Osf: 2, W _{s}: 1120 × 940,W _{p}: 150 × 125,S _{s}: 3000 × 2500 | Osf: none, W _{s}: 1000 × 1000,W _{p}: 240 × 200,Flow-dependent search window size | Osf: 2, W _{s}: 480 × 600,W _{p}: 90 × 112 | Osf: 8, W _{s}: 720 × 300,W _{p}: 150 × 60,S _{s}: 240 × 100 | Osf: 2, W _{s}: 960 × 800,W _{p}: 150 × 150 | Osf: 2, W _{s}: 180 × 80,480 × 200, 1440 × 600, 3 × 3 multi-look W _{p}: 180 × 80 | Osf: 2, W _{s}: 960 × 400,W _{p}: 150 × 60Flow dependent window position |

Outlier culling ^{d} | SNR_{thr} = 7.0,Max. velocity | SNR_{thr} = 1.8,Max. velocity, Local variability (mag. and dir.) | Median filter, Coastline mask | SNR_{thr} = 4.0,Unclear | NCC_{thr} = 0.04 | SNR_{thr} = 7.0,Max. velocity | NCC_{thr} = 0.07, 0.18,Median filter, Coastline mask | SNR_{thr} = 7.0,NCC _{thr} = 0.05, |

Filtering | Moving average | - | - | Ionospheric | - | - | Moving average | Moving average |

Geophysical inversion | Stationary GCPs | - | Stationary GCPs | High-SNR GCPs | - | Stationary GCPs | Stationary GCPs | Stationary GCPs |

Geocoding ^{e} | EQA, 280 m × 250 m | PS, 100 m × 100 m | PS, 150 m × 150 m | PS, 90 m × 90 m | PS, 90 m × 90 m | PS, 250 m × 250 m | PS, 200 m × 200 m | PS, 250 m × 250 m |

^{a}ACC: Amplitude cross-correlation, CCC: Complex cross-correlation, ICC: Intensity cross-correlation;

^{b}σ: per-pixel error standard deviation (m/y), NCC: normalized cross-correlation, SNR: cross-correlation peak Signal to Noise Ratio;

^{c}Osf: oversampling factor, W

_{s}, W

_{p}: cross-correlation window size and spacing respectively in m (ground range × azimuth), S

_{s}: search window size in m (ground range × azimuth);

^{d}SNR

_{thr}: SNR threshold, NCC

_{thr}: NCC threshold.

^{e}EQA: lat/lon grid, PS: NSIDC Polar Stereographic North (EPSG 3413).

Station | Component | Group | |||||||
---|---|---|---|---|---|---|---|---|---|

G1 | G2 | G3 | G4 | G5 | G6 | G7 | G8 | ||

SAR–GPS | |||||||||

N ^{a} | LoS | 2 | 3 | 3 | 1 | 3 | 1 | 3 | 2 |

Azimuth | 2 | 3 | 3 | 1 | 3 | 1 | 3 | 2 | |

Median ^{b} | LoS | −3.22 | −1.90 | −16.1 | −9.84 | −14.1 | 27.8 | 34.4 | 2.4 |

Azimuth | −21.2 | −5.4 | −23.7 | −10.6 | 13.6 | 20.1 | 2.63 | −8.39 | |

MAD ^{c} | LoS | 36.3 | 17.0 | 11.6 | - | 23.4 | - | 22.0 | 22.2 |

Azimuth | 43.9 | 23.3 | 19.1 | - | 22.7 | - | 17.6 | 41.2 | |

Bedrock | |||||||||

Median ^{b} | LoS | −0.71 | −0.28 | −0.26 | −0.91 | - | −1.05 | 0.6 | −0.22 |

Azimuth | −4.86 | −8.13 | −1.0 | −0.63 | - | −2.46 | 0.56 | −1.13 | |

MAD ^{c} | LoS | 1.83 | 3.57 | 1.21 | 4.01 | - | 2.36 | 1.57 | 0.92 |

Azimuth | 8.43 | 7.38 | 6.55 | 3.13 | - | 6.66 | 5.59 | 6.43 |

^{a}Number of co-located SAR and GPS measurements;

^{b}Median of SAR-GPS differences in m/y;

^{c}Median absolute deviation of SAR-GPS differences in m/y.

© 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Merryman Boncori, J.P.; Langer Andersen, M.; Dall, J.; Kusk, A.; Kamstra, M.; Bech Andersen, S.; Bechor, N.; Bevan, S.; Bignami, C.; Gourmelen, N.;
et al. Intercomparison and Validation of SAR-Based Ice Velocity Measurement Techniques within the Greenland Ice Sheet CCI Project. *Remote Sens.* **2018**, *10*, 929.
https://doi.org/10.3390/rs10060929

**AMA Style**

Merryman Boncori JP, Langer Andersen M, Dall J, Kusk A, Kamstra M, Bech Andersen S, Bechor N, Bevan S, Bignami C, Gourmelen N,
et al. Intercomparison and Validation of SAR-Based Ice Velocity Measurement Techniques within the Greenland Ice Sheet CCI Project. *Remote Sensing*. 2018; 10(6):929.
https://doi.org/10.3390/rs10060929

**Chicago/Turabian Style**

Merryman Boncori, John Peter, Morten Langer Andersen, Jørgen Dall, Anders Kusk, Martijn Kamstra, Signe Bech Andersen, Noa Bechor, Suzanne Bevan, Christian Bignami, Noel Gourmelen,
and et al. 2018. "Intercomparison and Validation of SAR-Based Ice Velocity Measurement Techniques within the Greenland Ice Sheet CCI Project" *Remote Sensing* 10, no. 6: 929.
https://doi.org/10.3390/rs10060929