= TestF3G - Navigation Error Sensitivity Test Results =
== Definitions ==
||'''CompareOBJ RMS:'''||The root mean square of the distance from each bigmap pixel/line location to the nearest facet of the truth OBJ.||
||'''PTG:'''||The formal camera pointing uncertainty.||
||'''SCOBJ:'''||The S/C position vector from the center of the asteroid.||
||'''VSO:'''||The formal SCOBJ uncertainty.||
== Additional Tests ==
=== S/C Position and Camera Pointing Uncertainties ===
The Detailed Survey PolyCam F3G data set had large S/C position and pointing uncertainties, unsuitable for Detailed Survey Baseball Diamond trajectories:
* VSO = 1km;
* PTG = 1mrad.
An additional suite of tests was therefore run with a duplicate Detailed Survey PolyCam dataset with S/C position and pointing uncertainties set to one-sigma:
* VSO = 6.4m;
* PTG = 0.217mrad.
Results for both data sets are presented herein.
=== Model Center-of-Body Shift ===
In the process of generating the 35cm Preliminary Shape Model, a shift in the body center with respect to the inertial center was applied. The magnitude of the shift was approximately 2m. Since the final S/C position across F3G subtests lay in a region 2m to 8m from the true S/C position, the effect of the body center shift came into question. To investigate, an alternative 35cm Preliminary Shape Model with no body-center shift was generated. One subtest was re-run using the alternative start model.
== Key Findings ==
CompareOBJ RMSs (with and without translation/rotation) show no trend with the magnitude of S/C position and camera pointing perturbation within the perturbation ranges tested. The correlation score also does not vary with the magnitude of S/C position and camera pointing perturbation and is approx. 0.76 giving a very good indication of correlation. The accuracy of the evaluation model is therefore invariant to the S/C position or camera pointing perturbation up to three standard deviations.
The results show no significant difference in the final S/C position (SCOBJ) with respect to the magnitude of S/C position and camera pointing perturbation within the ranges tested, indicating that the SPC-driven S/C position modeling is immune to S/C position and pointing perturbation up to three standard deviations.
With the large S/C position and camera pointing uncertainties, the final SPC-derived S/C position is within 8m of the true S/C position, and in two cases is within 2m of the true S/C position. With the reduced (1 sigma) S/C position and camera pointing uncertainties, all the final SPC-derived S/C positions are within 2m of the true S/C position. The distance between the final S/C position and the true S/C position is not dependent on the initial perturbed S/C position - indeed, in the 0.25 x sigma case, the SPC-derived S/C position in most cases moves further away from the true S/C position (final distance from truth: 1.6m to 6.9m) than its initial position (initial distance from truth: 1.6m).
The final SPC-derived S/C positions appear to be clustered around an incorrect solution 2m distant from the true S/C position (in the VSO=1sigma tests). This distance appears to correspond with a shift in the center-of-body which was applied during the generation of the 35cm Preliminary Survey Start Model. However, this finding persisted when a subtest was re-run with a 35cm Preliminary Survey Start Model which had not had a shift applied to the center-of-body. Measures of both model accuracy and S/C position did not vary with center-of-body shift.
== Important Notes ==
It should be noted that S/C position perturbation was divided equally between the SCOBJ components, resulting in a distance from the truth position which was a multiple of the standard deviation of 6.4m. Therefore:
* maximum lateral perturbation was a multiple of 3.7m (6.4m/sqrt(3));
* maximum normal perturbation (wrt body center) was a multiple of 3.7m (6.4m/sqrt(3)).
It is assumed that the worst case scenario is a 3 x sigma (19.2m) lateral perturbation. The maximum possible lateral perturbation tested was 3 x 3.7m = 11.1m.
== Results and Discussion ==
=== CompareOBJ RMS ===
Three CompareOBJ RMS values for the final 5cm resolution 20m x 20m evaluation bigmap are presented for each subtest and each S/C position and camera pointing uncertainty:
* The largest CompareOBJ RMS (approx. 65cm across subtests) is obtained by running CompareOBJ on the untranslated and unrotated evaluation model.
* The second smallest CompareOBJ RMS (approx. 15cm across subtests) is obtained by running CompareOBJ with its optimal translation and rotation option.
* The smallest CompareOBJ RMS (approx. 9cm across subtests) is obtained by manually translating the evaluation model and searching for a local CompareOBJ RMS minimum.
The CompareOBJ optimal translation routine is not optimized for the evaluation model scale (5cm pix/line resolution). Manual translations of the bigmap were therefore conducted in an attempt to find a minimum CompareOBJ RMS. The manually translated evaluation models gave the smallest CompareOBJ RMSs.
CompareOBJ RMSs do not show a trend with the magnitude of S/C position and pointing perturbation within the ranges tested.
CompareOBJ RMSs differ slightly with S/C position and camera pointing uncertainties, with smaller RMS values corresponding with lower uncertainties:
* approx. 5cm difference for CompareOBJ RMS without translation/rotation;
* approx. 2cm difference for CompareOBJ RMS with optimal translation and rotation;
* approx. 0.4cm difference for CompareOBJ RMS with manual translation.
{{attachment:CompareOBJ_VSO_1km_resized60pt.png}}
{{attachment:CompareOBJ_VSO_1sigma_resized60pt.png}}
'''CompareOBJ Optimal Translations:'''
||'''Sub-Test'''||'''S/C Position Uncertainty'''||'''Perturbation Magnitude'''||'''RMS (cm)'''||||||'''Translation (cm)'''||'''Translated Distance (cm)'''||
||F3G7a||1km||0.25 x sigma||15.7849||85.0698||62.3596||-14.3765||106.4532||
||F3G6a||1km||0.50 x sigma||15.1147||84.5538||61.6624||-15.3434||105.7687||
||F3G5a||1km||0.75 x sigma||14.3150||95.8438||59.9313||-21.6901||115.1011||
||F3G3a||1km||1.00 x sigma||13.6399||106.4870||58.2162||-27.3527||124.4057||
||F3G4a||1km||1.50 x sigma||15.8949||79.1224||63.2865||-19.6432||103.2056||
||F3G2a||1km||2.00 x sigma||13.6938||110.1339||58.9454||-23.2403||127.0596||
||F3G1a||1km||3.00 x sigma||14.6271||93.5937||61.6997||-26.8422||115.2698||
||'''Sub-Test'''||'''S/C Position Uncertainty'''||'''Perturbation Magnitude'''||'''RMS (cm)'''||||||'''Translation (cm)'''||'''Translated Distance (cm)'''||
||F3G7b||6.4m||0.25 x sigma||15.9614||95.5555||66.8688||-17.6793||117.9613||
||F3G6b||6.4m||0.50 x sigma||16.0260||93.7254||66.9687||-17.2331||116.4743||
||F3G5b||6.4m||0.75 x sigma||16.4387||88.3626||69.0785||-12.1628||112.8172||
||F3G3b||6.4m||1.00 x sigma||9.5449||167.5406||57.3951||-27.0780||179.1571||
||F3G4b||6.4m||1.50 x sigma||16.0525||93.4737||70.0956||-15.0998||117.808=1||
||F3G2b||6.4m||2.00 x sigma||16.1591||94.1139||69.1165||-19.95051||118.4514||
||F3G1b||6.4m||3.00 x sigma||15.2938||101.8134||70.3467||-20.3179||125.4091||
'''CompareOBJ Manual Translations:'''
||'''Sub-Test'''||'''S/C Position Uncertainty'''||'''Perturbation Magnitude'''||'''RMS (cm)'''||||||'''Translation (cm)'''||'''Translated Distance (cm)'''||
||F3G7a||1km||0.25 x sigma||8.0140||187.5||47.5||-30||195.74||
||F3G6a||1km||0.50 x sigma||7.9343||187.5||47.5||-30||195.74||
||F3G5a||1km||0.75 x sigma||7.9579||187.5||47.5||-30||195.74||
||F3G3a||1km||1.00 x sigma||7.6749||187.5||47.5||-30||195.74||
||F3G4a||1km||1.50 x sigma||7.9964||187.5||47.5||-40||197.52||
||F3G2a||1km||2.00 x sigma||7.8591||187.5||47.5||-40||197.52||
||F3G1a||1km||3.00 x sigma||7.6739||187.5||47.5||-50||209.19||
||'''Sub-Test'''||'''S/C Position Uncertainty'''||'''Perturbation Magnitude'''||'''RMS (cm)'''||||||'''Translation (cm)'''||'''Translated Distance (cm)'''||
||F3G7b||6.4m||0.25 x sigma||8.4097||207.5||47.5||-30||214.9709||
||F3G6b||6.4m||0.50 x sigma||8.3974||207.5||47.5||-30||214.9709||
||F3G5b||6.4m||0.75 x sigma||8.5008||207.5||47.5||-30||214.9709||
||F3G3b||6.4m||1.00 x sigma||8.2400||207.5||47.5||-40||216.5929||
||F3G4b||6.4m||1.50 x sigma||8.5820||197.5||57.5||-20||206.6700||
||F3G2b||6.4m||2.00 x sigma||8.4134||197.5||57.5||-30||207.8762||
||F3G1b||6.4m||3.00 x sigma||7.9259||197.5||57.5||-30||207.8762||
=== Normalized Cross Correlation Scores ===
The evaluation maps were compared with a truth map via a cross-correlation routine which derives a correlation score. As a guide the following scores show perfect and excellent correlations:
* A map cross-correlated with itself will give a correlation score of approx. 1.0;
* Different sized maps sampled from the same truth (for example a 1,100 x 1,100 5cm sample map and a 1,000 x 1,000 5cm sample map) give a correlation score of approx. 0.8.
The correlation scores show no trend with S/C position and camera pointing perturbation in the perturbation-range tested. The correlation scores also do not differ with S/C position and camera pointing uncertainties. The correlation score across subtests is approx. 0.76 giving a very good indication of correlation.
'''Correlation Scores:'''
||'''Sub-Test'''||'''S/C Position Uncertainty'''||'''Perturbation Magnitude'''||'''Correlation Score'''||
||F3G7a||1km||0.25 x sigma||0.7619||
||F3G6a||1km||0.50 x sigma||0.7625||
||F3G5a||1km||0.75 x sigma||0.7617||
||F3G3a||1km||1.00 x sigma||0.7641||
||F3G4a||1km||1.50 x sigma||0.7684||
||F3G2a||1km||2.00 x sigma||0.7537||
||F3G1a||1km||3.00 x sigma||0.7679||
||'''Sub-Test'''||'''S/C Position Uncertainty'''||'''Perturbation Magnitude'''||'''Correlation Score'''||
||F3G7b||6.4m||0.25 x sigma||0.7628||
||F3G6b||6.4m||0.50 x sigma||0.7633||
||F3G5b||6.4m||0.75 x sigma||0.7637||
||F3G3b||6.4m||1.00 x sigma||0.7672||
||F3G4b||6.4m||1.50 x sigma||0.7606||
||F3G2b||6.4m||2.00 x sigma||0.7510||
||F3G1b||6.4m||3.00 x sigma||0.7683||
=== Image Footprints ===
The first graph shows footprints for all Detailed Survey PolyCam pictures which were included in the model. The second graph shows the four pictures down-selected for S/C position evaluation purposes due to their coverage of the 20m x 20m evaluation region, and their almost complete containment within the iterated 100m x 100m region.
{{attachment:vertices_all_resized.png}}
{{attachment:vertices_eval_resized.png}}
=== Distance SCOBJ(truth) to SCOBJ(solution) ===
The distance of the final SPC-derived S/C position from the true S/C position is plotted for the evaluation Detailed Survey PolyCam image set for each magnitude of perturbation. The distance of the final SCOBJ from the true S/C position is invariant with the perturbation to the initial SCOBJ within the perturbation-range tested. The range of distances across pictures does vary with S/C position uncertainty however, with:
* distances ranging from approx. 1m to 8m with VSO=1km;
* distances ranging from approx. 1m to 2m with VSO=6.4m (1 sigma).
{{attachment:SCOBJ_distance_VSO_1km_resized60pct.png}}
{{attachment:SCOBJ_distance_VSO_1sigma_resized60pct.png}}
=== SCOBJ ===
3D graphs of final SPC-derived SCOBJ and true SCOBJ are plotted for each evaluation picture.
The pattern of final SPC-derived SCOBJ is broadly consistent across magnitudes of initial S/C position perturbation. The position correction is mostly a normal correction with lateral movement, bringing the modeled S/C position within approx. 2m to 8m of the true S/C position. Note that the SCOBJs form a cluster which is offset from the truth indicating that the model is converging to a solution different to the truth.
==== Evaluation Pictures ====
'''Example nominal SCOBJs:'''
{{attachment:P601293751G3_nominal_resized.png}}
''' Final solution SCOBJs:'''
{{attachment:P601293751G3_All_resized_40pct.png}}
{{attachment:P601372862G2_All_resized_40pct.png}}
{{attachment:P601372868G2_All_resized_40pct.png}}
{{attachment:P601372874G2_All_resized_40pct.png}}
=== SCOBJ without center-of-body shift ===
3D graphs of final SPC-derived SCOBJ and true SCOBJ are re-plotted for each evaluation picture, now including the single result from the additional subtest conducted from a 35cm Preliminary Survey Start Model with no center-of-body shift. The graphs show that the final SCOBJ is not affected by center-of-body shift up to 2m. This result also dispels the notion that the distance of the final SCOBJs from truth is connected to the center-of-body shift.
{{attachment:P601293751G3_woShift_resized_40pct.png}}
{{attachment:P601372862G2_woShift_resized_40pct.png}}
{{attachment:P601372868G2_woShift_resized_40pct.png}}
{{attachment:P601372874G2_woShift_resized_40pct.png}}