How GSD and carrier drone types affect the relative accuracy of 3D model

In the last article How ground control points and PPK data affect the relative accuracy of 3D model,we have mentioned that in addition to GCPs and PPK datas, the GSD and carrier drone also have a certain degree of effects on the relative accuracy of the 3D model.So we do another test to verify it.

Experiment 1: the effect of GSD on the relative accuracy of the 3D model;

Condition 1

Carrier drone	Oblique camera	GCPs	PPK
CW10 VTOL	DG4pros	NO	NO

Result Table 1:

Number of Objects	measurement length（L0）	3D model length（L1）GSD=2cm	3D model length（L2）GSD=1.5cm	DS1（L0-L1）	DS2（L0-L2）
1	7.210	7.18	7.20	0.030	0.010
	8.706	8.69	8.65	0.016	0.056
	10.961	10.89	10.90	0.071	0.061
2	7.010	6.88	6.86	0.130	0.150
3	1.822	1.76	1.76	0.062	0.062
4	10.410	10.38	10.37	0.030	0.040
5	10.718	10.65	10.68	0.068	0.038
6	13.787	13.72	13.71	0.067	0.077
7	11.404	11.41	11.38	-0.006	0.024
	12.147	12.13	12.12	0.017	0.027
8	7.526	7.44	7.49	0.086	0.036
	13.797	13.83	13.77	-0.033	0.027
9	10.374	10.35	10.35	0.024	0.024
10	2.109	1.98	2.09	0.129	0.019
	4.281	4.14	4.19	0.141	0.091
11	14.675	14.55	14.64	0.125	0.035
	8.600	8.58	8.57	0.020	0.030
12	13.394	13.36	13.38	0.034	0.014
13	12.940	12.95	12.91	-0.010	0.030
14	7.190	7.21	7.20	-0.020	-0.010
15	13.371	13.36	13.38	0.011	-0.009
	6.435	6.37	6.43	0.065	0.005
16	3.742	3.74	3.70	0.002	0.042
17	6.022	6.03	5.99	-0.008	0.032
18	3.937	3.91	3.94	0.027	-0.003
19	8.120	8.09	8.12	0.030	0.000
	14.411	14.40	14.37	0.011	0.041
20	6.077	6.06	6.04	0.017	0.037
21	13.696	13.68	13.65	0.016	0.046
RMSE： DS1=0.0397m，DS2=0.0356m

Condition 2

Carrier drone	Oblique camera	GCPs	PPK
CW10 VTOL	DG4pros	Yes	No

Result Table 2:

Number of Objects	measurement length（L0）	3D model length（L1）GSD=2cm	3D model length（L2）GSD=1.5cm	DS1（L0-L1）	DS2（L0-L2）
1	7.210	7.18	7.21	0.030	0
	8.706	8.68	8.68	0.026	0.026
	10.961	10.91	10.87	0.051	0.091
2	7.010	6.92	6.88	0.090	0.13
3	1.822	1.79	1.76	0.032	0.062
4	10.410	10.39	10.38	0.020	0.03
5	10.718	10.66	10.72	0.058	-0.002
6	13.787	13.77	13.79	0.017	-0.003
7	11.404	11.38	11.38	0.024	0.024
	12.147	12.12	12.13	0.027	0.017
8	7.526	7.47	7.53	0.056	-0.004
	13.797	13.83	13.78	-0.033	0.017
9	10.374	10.34	10.37	0.034	0.004
10	2.109	2.03	2.11	0.079	-0.001
	4.281	4.18	4.28	0.101	0.001
11	14.675	14.59	14.67	0.085	0.005
	8.600	8.57	8.58	0.030	0.02
12	13.394	13.35	13.39	0.044	0.004
13	12.940	12.92	12.9	0.020	0.04
14	7.190	7.21	7.19	-0.020	0
15	13.371	13.36	13.37	0.011	0.001
	6.435	6.43	6.42	0.005	0.015
16	3.742	3.72	3.7	0.022	0.042
17	6.022	6.00	5.98	0.022	0.042
18	3.937	3.94	3.91	-0.003	0.027
19	8.120	8.09	8.07	0.030	0.05
	14.411	14.41	14.38	0.001	0.031
20	6.077	6.03	6.04	0.047	0.037
21	13.696	13.65	13.65	0.046	0.046
RMSE: DS1=0.0328m，DS2=0.0259m

Condition 3

Carrier drone	Oblique camera	GCPs	PPK
CW10 VTOL	DG4pros	NO	YES

Result Table 3:

Number of Objects	measurement length（L0）	3D model length（L1）GSD=2cm	3D model length（L2）GSD=1.5cm	DS1（L0-L1）	DS2（L0-L2）
1	7.210	7.20	7.20	0.01	0.01
	8.706	8.71	8.69	0.00	0.02
	10.961	10.87	10.88	0.09	0.08
2	7.010	6.89	6.87	0.12	0.14
3	1.822	1.79	1.75	0.03	0.07
4	10.410	10.39	10.38	0.02	0.03
5	10.718	10.67	10.69	0.05	0.03
6	13.787	13.75	13.78	0.04	0.01
7	11.404	11.39	11.38	0.01	0.02
	12.147	12.13	12.12	0.02	0.03
8	7.526	7.51	7.49	0.02	0.04
	13.797	13.79	13.78	0.01	0.02
9	10.374	10.35	10.34	0.02	0.03
10	2.109	2.03	2.02	0.08	0.09
	4.281	4.15	4.21	0.13	0.07
11	14.675	14.61	14.65	0.07	0.03
	8.600	8.60	8.57	0.00	0.03
12	13.394	13.37	13.40	0.02	-0.01
13	12.940	12.88	12.89	0.06	0.05
14	7.190	7.20	7.18	-0.01	0.01
15	13.371	13.36	13.38	0.01	-0.01
	6.435	6.40	6.46	0.03	-0.03
16	3.742	3.75	3.75	-0.01	-0.01
17	6.022	5.97	5.97	0.05	0.05
18	3.937	3.93	3.91	0.01	0.03
19	8.120	8.10	8.08	0.02	0.04
	14.411	14.40	14.38	0.01	0.03
20	6.077	6.04	6.05	0.04	0.03
21	13.696	13.65	13.67	0.05	0.03
RMSE: DS1=0.0342m，DS2=0.0328m

Condition 4

Carrier drone	Oblique camera	GCPs	PPK
CW10 VTOL	DG4pros	YES	YES

Result Table 4:

Number of Objects	measurement length（L0）	3D model length（L1）GSD=2cm	3D model length（L2）GSD=1.5cm	DS1（L0-L1）	DS2（L0-L2）
1	7.21	7.21	7.21	0.00	0.00
	8.706	8.68	8.7	0.03	0.01
	10.961	10.90	10.89	0.06	0.07
2	7.01	6.98	6.99	0.03	0.02
3	1.822	1.80	1.78	0.02	0.04
4	10.41	10.40	10.39	0.01	0.02
5	10.718	10.70	10.69	0.02	0.03
6	13.787	13.77	13.76	0.02	0.03
7	11.404	11.39	11.39	0.01	0.01
7	12.147	12.13	12.12	0.02	0.03
8	7.526	7.49	7.51	0.04	0.02
8	13.797	13.81	13.8	-0.01	0.00
9	10.374	10.36	10.35	0.01	0.02
10	2.109	2.02	2.11	0.09	0.00
10	4.281	4.16	4.28	0.12	0.00
11	14.675	14.66	14.68	0.02	0.00
11	8.6	8.54	8.53	0.06	0.07
12	13.394	13.35	13.37	0.04	0.02
13	12.94	12.89	12.91	0.05	0.03
14	7.19	7.18	7.2	0.01	-0.01
15	13.371	13.35	13.35	0.02	0.02
15	6.435	6.41	6.4	0.02	0.03
16	3.742	3.72	3.71	0.02	0.03
17	6.022	5.98	5.98	0.04	0.04
18	3.937	3.89	3.89	0.05	0.05
19	8.12	8.12	8.1	0.00	0.02
19	14.411	14.40	14.39	0.01	0.02
20	6.077	6.03	6.03	0.05	0.05
21	13.696	13.66	13.64	0.04	0.06
RMSE： DS1=0.0308m，DS2=0.0249m

Conclusions

The variables of experiment 1 are:

1:With/Without PPK data.

2:With/Without GCPs.

3:different GSD：1.5 cm or 2cm

After analysis of the four sets of experimental data, we can draw the following conclusions:

When the oblique camera is DG4Pros:

(1) With/Without ground control point (GCP) and PPK data involved in the AT triangulation, whether it is a VTOL or a multi-rotor drone, whether the GSD is 2cm or 1.5cm, the 3D model built by oblique camera DG4Pros can meet the requirements of relative accuracy error Ds≤10cm(Actually ≤5cm).

(2) When the GSD is the single variable, the relative accuracy of the 3D model with GSD=1.5cm is better than that GSD=2cm.

Experiment 2: the effect of carrier drone types on the relative accuracy of the 3D model

Condition 1

Oblique camera	GCPs	PPK	GSD
DG4pros	NO	NO	1.5cm

Result Table 1:

Number of Objects	measurement length（L0）	3D model length（L1）CW10	3D model length（L2）M600Pro	DS1（L0-L1）	DS2（L0-L2）
1	7.21	7.20	7.19	0.010	0.02
	8.706	8.65	8.70	0.056	0.01
	10.961	10.90	10.91	0.061	0.05
2	7.01	6.86	6.98	0.150	0.03
3	1.822	1.76	1.79	0.062	0.03
4	10.41	10.37	10.39	0.040	0.02
5	10.718	10.68	10.69	0.038	0.03
6	13.787	13.71	13.76	0.077	0.03
7	11.404	11.38	11.38	0.024	0.02
	12.147	12.12	12.12	0.027	0.03
8	7.526	7.49	7.50	0.036	0.03
	13.797	13.77	13.77	0.027	0.03
9	10.374	10.35	10.33	0.024	0.04
10	2.109	2.09	2.02	0.019	0.09
	4.281	4.19	4.20	0.091	0.08
11	14.675	14.64	14.65	0.035	0.03
	8.6	8.57	8.57	0.030	0.03
12	13.394	13.38	13.35	0.014	0.04
13	12.94	12.91	12.92	0.030	0.02
14	7.19	7.20	7.17	-0.010	0.02
15	13.371	13.38	13.35	-0.009	0.02
	6.435	6.43	6.41	0.005	0.02
16	3.742	3.70	3.70	0.042	0.04
17	6.022	5.99	5.99	0.032	0.03
18	3.937	3.94	3.89	-0.003	0.05
19	8.12	8.12	8.08	0.000	0.04
	14.411	14.37	14.36	0.041	0.05
20	6.077	6.04	6.06	0.037	0.02
21	13.696	13.65	13.65	0.046	0.05
RMSE: DS1=0.0356m，DS2=0.342m

Condition 2

Oblique camera	GCPs	PPK	GSD
DG4pros	YES	NO	1.5cm

Result Table 2:

Number of Objects	measurement length（L0）	3D model length（L1）CW10	3D model length（L2）M600Pro	DS1（L0-L1）	DS2（L0-L2）
1	7.21	7.21	7.21	0	0.00
	8.706	8.68	8.70	0.026	0.01
	10.961	10.87	10.91	0.091	0.05
2	7.01	6.88	6.98	0.13	0.03
3	1.822	1.76	1.80	0.062	0.02
4	10.41	10.38	10.39	0.03	0.02
5	10.718	10.72	10.70	-0.002	0.02
6	13.787	13.79	13.75	-0.003	0.04
7	11.404	11.38	11.38	0.024	0.02
	12.147	12.13	12.13	0.017	0.02
8	7.526	7.53	7.49	-0.004	0.04
	13.797	13.78	13.79	0.017	0.01
9	10.374	10.37	10.35	0.004	0.02
10	2.109	2.11	2.07	-0.001	0.04
	4.281	4.28	4.21	0.001	0.07
11	14.675	14.67	14.66	0.005	0.02
	8.6	8.58	8.57	0.02	0.03
12	13.394	13.39	13.35	0.004	0.04
13	12.94	12.9	12.93	0.04	0.01
14	7.19	7.19	7.18	0	0.01
15	13.371	13.37	13.36	0.001	0.01
	6.435	6.42	6.42	0.015	0.01
16	3.742	3.7	3.71	0.042	0.03
17	6.022	5.98	6.00	0.042	0.02
18	3.937	3.91	3.91	0.027	0.03
19	8.12	8.07	8.10	0.05	0.02
	14.411	14.38	14.35	0.031	0.06
20	6.077	6.04	6.06	0.037	0.02
21	13.696	13.65	13.67	0.046	0.03
RMSE: DS1=0.0259m，DS2=0.256m

Conclusions

The variables of experiment 2 are:

1:With/Without GCPs.

2:Different Carrier drone:a VTOL drone or a multi-rotor drone

After analysis of the two sets of experimental data, we can draw the following conclusions:

When the oblique camera is DG4Pros:

(1) With/Without ground control point (GCP) whether it is a VTOL or a multi-rotor drone, the 3D model built by oblique camera DG4Pros can meet the requirements of relative accuracy error Ds≤10cm(Actually ≤5cm).

(2) When the carrier drone types is the single variable, the relative accuracy of the 3D model with multi-rotor is better than that with VTOL,but the difference is not very big.

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