Differences In View Angles Research Articles

A coupled ground heat flux–surface energy balance model of evaporation using thermal remote sensing observations

Abstract. One of the major undetermined problems in evaporation (ET) retrieval using thermal infrared remote sensing is the lack of a physically based ground heat flux (G) model and its integration within the surface energy balance (SEB) equation. Here, we present a novel approach based on coupling a thermal inertia (TI)-based mechanistic G model with an analytical surface energy balance model, Surface Temperature Initiated Closure (STIC, version STIC1.2). The coupled model is named STIC-TI. The model is driven by noon–night (13:30 and 01:30 local time) land surface temperature, surface albedo, and a vegetation index from MODIS Aqua in conjunction with a clear-sky net radiation sub-model and ancillary meteorological information. SEB flux estimates from STIC-TI were evaluated with respect to the in situ fluxes from eddy covariance measurements in diverse ecosystems of contrasting aridity in both the Northern Hemisphere and Southern Hemisphere. Sensitivity analysis revealed substantial sensitivity of STIC-TI-derived fluxes due to the land surface temperature uncertainty. An evaluation of noontime G (Gi) estimates showed 12 %–21 % error across six flux tower sites, and a comparison between STIC-TI versus empirical G models also revealed the substantially better performance of the former. While the instantaneous noontime net radiation (RNi) and latent heat flux (LEi) were overestimated (15 % and 25 %), sensible heat flux (Hi) was underestimated (22 %). Overestimation (underestimation) of LEi (Hi) was associated with the overestimation of net available energy (RNi−Gi) and use of unclosed surface energy balance flux measurements in LEi (Hi) validation. The mean percent deviations in Gi and Hi estimates were found to be strongly correlated with satellite day–night view angle difference in parabolic and linear pattern, and a relatively weak correlation was found between day–night view angle difference versus LEi deviation. Findings from this parameter-sparse coupled G–ET model can make a valuable contribution to mapping and monitoring the spatiotemporal variability of ecosystem water stress and evaporation using noon–night thermal infrared observations from future Earth observation satellite missions such as TRISHNA, LSTM, and SBG.

Multi-Camera Vehicle Tracking Based on Deep Tracklet Similarity Network

Multi-camera vehicle tracking at the city scale has received lots of attention in the last few years. It has large-scale differences, frequent occlusion, and appearance differences caused by the viewing angle differences, which is quite challenging. In this research, we propose the Tracklet Similarity Network (TSN) for a multi-target multi-camera (MTMC) vehicle tracking system based on the evaluation of the similarity between vehicle tracklets. In addition, a novel component, Candidates Intersection Ratio (CIR), is proposed to refine the similarity. It provides an associate scheme to build the multi-camera tracking results as a tree structure. Based on these components, an end-to-end vehicle tracking system is proposed. The experimental results demonstrate that an 11% improvement on the evaluation score is obtained compared to the conventional similarity baseline.

Radiometric Performance Evaluation of FY-4A/AGRI Based on Aqua/MODIS.

Fengyun-4A (FY-4A) is the first satellite of the Chinese second-generation geostationary orbit meteorological satellites (FY-4). The Advanced Geostationary Radiation Imager (AGRI), onboard FY-4A does not load with high-precision calibration facility in visible and near infrared (VNIR) channel. As a consequence, it is necessary to comprehensively evaluate its radiometric performance and quantitatively describe the attenuation while using its VNIR data. In this paper, the radiometric performance at VNIR channels of FY-4A/AGRI is evaluated based on Aqua/MODIS data using the deep convective cloud (DCC) target. In order to reduce the influence of view angle and spectral response difference, the bi-directional reflectance distribution function (BRDF) correction and spectral matching have been performed. The evaluation result shows the radiometric performance of FY-4A/AGRI: (1) is less stable and with obvious fluctuations; (2) has a lower radiation level because of 24.99% lower compared with Aqua/MODIS; 3) has a high attenuation with 9.11% total attenuation over 2 years and 4.0% average annual attenuation rate. After the evaluation, relative radiometric normalization between AGRI and MODIS in VNIR channel is performed and the procedure is proved effective. This paper proposed a more reliable reference for the quantitative applications of FY-4A data.

Computerised Tomography Analysis of Pelvic Inlet and Outlet Fluoroscopic View Angles.

Pelvic inlet and outlet fluoroscopy views are routinely used in operative treatment of posterior pelvic ring injuries. In this study, we aimed to evaluate the angles of pelvic inlet and outlet fluoroscopic view, their differences with hip flexion and the correlation of these differences with sacral slope changes. Sagittal reconstructions of 100 lumbopelvic CT were used to measure sacral slope, pelvic inlet and outlet view angles. The range of pelvic inlet-outlet view angles and their relation with age, sex and sacral slope were analyzed. In ten of these 100 patients, who were undergone a second CT imaging, hips were passively flexed to 60° to change pelvic tilt. The difference in sacral slope and pelvic inlet-outlet view angles in different positions were compared. Mean angles for inlet view, outlet view and sacral slope were 28.9, 41.4 and 37.0, respectively. There was no difference between males and females (p > 0.05). Pelvic outlet angles had a negative correlation with age (p < 0.05). Sacral slope changes with hip flexion showed a negative correlation with inlet angles and positive correlation with outlet angles (p < 0.05). The differences in sacral slope, pelvic inlet and outlet view angles between two measurements were equal. The pelvic inlet and outlet view angles shows a wide range without a standard so we suggest preoperative CT scan to plan the optimal angles before pelvic ring surgery. The difference in these angles due to pelvic tilt during the surgery may be corrected by measuring the sacral slope difference.

Universal algorithm for water depth refraction correction in through-water stereo remote sensing

In through-water stereo remote sensing, the correction of the effect of light refraction on water depth determination is an unsolved problem. The challenge is that no solution exists for apparent positions when the conjugate image rays are non-intersecting. This paper proposes a new water depth refraction correction algorithm for through-water stereo remote sensing. The midpoint of the shortest line segment between two non-intersecting conjugate image rays is used as the apparent position, so that the mathematical relationship between the apparent and actual depths is established under the “no solution condition”. The new algorithm is reasonable and applicable whether or not conjugate image rays are intersecting. Compared with the existing algorithms, the new algorithm can improve bathymetric accuracy in different degrees. The improvement becomes more significant as the off-nadir view angle difference and the depth increase. Results for Area 1 showed that, compared with the three existing algorithms, the new algorithm improved RMSE accuracy by about 22%, 29% and 24% respectively. The new algorithm enables reasonable water depth refraction correction to be implemented in any case (whether conjugate image rays are intersecting or not).

Hand-in-Air (HiA) and Hand-on-Target (HoT) Style Gesture Cues for Mixed Reality Collaboration

In collaboration systems, collaborators often use hand gestures for showing information relating to a distant object. However, in viewer’s perspective, it is sometimes difficult to know where the conventional gesture cue (Hands-in-Air style: HiA) refers to because the conventional HiA gesture appears away from the distant object. In this paper, we investigate how two factors, distance to the object and view angle difference between collaborators, influence the understanding of HiA gesture by comparing the use of it at 25 positions with 5 distances and 5 view angles. In a user study, we found that the distance to the target object and view angle difference negatively influenced HiA gesture communication. The influence of the distance and view angle was more serious between smaller angles (0~30 degree) than larger angles (30~60 degree), and between shorter distances (1m $\sim 1.5\text{m}$ ) than between longer distance (1.5m $\sim 2\text{m}$ ). As a solution, we propose the Hands-on-Target (HoT) style which positions the hand gesture cue on the surface of the target object. The HoT style gesture cue dramatically reduces the negative effect of the distance and view angle difference. Participants completed the task 29.3 percent faster, selected the correct object 2.75 times more, and felt 63.1 percent less mental effort. For further investigation, we discuss on the extensibility of the HoT interface that it can be used not only for object selection but also for diverse type of gesture communication including gesture for object manipulation because the HoT interface can support all possible real world hand gestures.

Aqua and Terra MODIS RSB calibration comparison using BRDF modeled reflectance.

The inter-comparison of MODIS reflective solar bands onboard Aqua and Terra is very important for assessment of each instrument's calibration. One of the limitations is the lack of simultaneous nadir overpasses. Their measurements over a selected Earth view target have significant differences in solar and view angles, which magnify the effects of atmospheric scattering and Bidirectional Reflectance Distribution Function (BRDF). In this work, an inter-comparison technique is formulated after correction for site's BRDF and atmospheric effects. The reflectance measurements over Libya desert sites 1, 2, and 4 from both the Aqua and Terra MODIS are regressed to a BRDF model with an adjustable coefficient accounting for calibration difference. The ratio between Aqua and Terra reflectance measurements are derived for bands 1 to 9 and the results from different sites show good agreement. For year 2003, the ratios are in the range of 0.985 to 1.010 for band 1 to 9. Band 3 shows the lowest ratio 0.985 and band 1shows the highest ratio 1.010. For the year 2014, the ratio ranges from approximately 0.983 for bands 2 and 1.012 for band 8. The BRDF corrected reflectance for the two instruments are also derived for every year from 2003 to 2014 for stability assessment. Bands 1 and 2 show greater than 1% differences between the two instruments. Aqua bands 1 and 2 show downward trends while Terra bands 1 and 2 show upward trends. Bands 8 and 9 of both Aqua and Terra show large variations of reflectance measurement over time.

Building Change Detection Improvement Using Topographic Correction Models

In the change detection application of remote sensing, commonly the variation in the brightness values of the pixels/objects in bi-temporal image is used as an indicator for detecting changes. However, there exist effects, other than a change in the objects that can cause variations in the brightness values. One of the effects is the illumination difference on steep surfaces mainly steeproofs of houses in very high resolution images, specifically in off-nadir images. This can introduce the problem of false change detection results. This problem becomes more serious in images with different view-angles. In this study, we propose a methodology to improve the building change detection accuracy using imagery taken under different illumination conditions and different view-angles. This is done by using the Patch-Wise Co-Registration (PWCR) method to overcome the misregistration problem caused by view-angle difference and applying Topographic Correction (TC) methods on pixel intensities to attenuate the effect of illumination angle variation on the building roofs. To select a proper TC method, four of the most widely used correction methods, namely C-correction, Minnaert, Enhanced Minnaert (for slope), and Cosine Correction are evaluated in this study. The results proved that the proposed methodology is capable to improve the change detection accuracy. Specifically, the correction using the C-correction and Enhanced Minnaert improved the change detection accuracy by around 35% in an area with a large number of steep-roof houses imaged under various solar angles.

Relative Radiometric Normalization for Multitemporal Remote Sensing Images by Hierarchical Regression

The existing relative radiometric normalization methods are insufficient to define the invariant pixels automatically, and the conventional methods do not perform well when the multitemporal images contain a lot of changes. Two types of changes should be particularly considered: one is caused by significant spectral differences due to change of ground objects, and the other is the pixels in the regions of misalignment caused by displacement due to differences in acquisition view angles and geometrical distortions. To automatically extract invariant pixels and reduce the influence of the changes, a hierarchical regression method is proposed to reduce the radiation difference for multitemporal images, which consists of extraction of the pseudo-invariant features (PIFs) and optimization of normalization parameters. A weighted regression based on spectral difference is proposed to automatically extract the PIFs, which can also suppress the negative effect of the first type of changes. In addition, a robust regression with gradient dependence is performed on the extracted PIFs to build the final relationship between the target image and the reference image, which can be robust for the second type of changes. Experimental results demonstrate that the proposed method has a better performance to normalize the target image.

Multimode image matching based on maximum similarity model and scale invariant feature transform for islands

Different from the images of villages or towns where many homologous features can be extracted easily, the extraction of homologous features from multimode images located of sea islands is more difficult because the types of objects on sea islands are hard to recognize. When applying scale invariant feature transform (SIFT) to the image matching of sea islands, only sparsely matched couples with an uneven distribution are obtained. To resolve this problem, a new feature point matching method that combines a maximum similarity model and scale invariant feature transform (MS-SIFT) is proposed. This method can solve the primary difficulty of matching multimode images, which is to extract the massive feature points that are invariant to differences in spectrum, scale, and view angles between multimode images, and successfully obtain many precise matched couples of images located in areas with less remarkable features, especially for matching images of sea islands with less features. The application of the proposed algorithm shows that a large number of accurately matched couples could be identified. Additionally, the matched accuracy, space uniformity of the matched couples, and the running time computed based on the MS-SIFT and the traditional SIFT are analyzed and compared, which further demonstrate the effectiveness of the proposed algorithm.

Inter-Comparison between VIIRS and MODIS Radiances and Ocean Color Data Products over the Chesapeake Bay

Since the October 2011 launch of the VIIRS (Visible Infrared Imaging Radiometer Suite) instrument, a number of inter-sensor comparisons between VIIRS and MODIS (Moderate Resolution Imaging Spectroradiometer) radiances have been reported. Most of these comparisons are between calibrated radiances and temperatures based on observations of the two sensors from simultaneous nadir overpasses (SNO). Few comparisons between the retrieved ocean color data products, such as chlorophyll concentration, from VIIRS and MODIS data have been reported. Retrievals from measured data at large solar zenith angles and large view zenith angles are excluded from these comparison studies. In this paper, we report the inter-sensor comparisons between VIIRS and MODIS data acquired over the Chesapeake Bay and nearby areas with relatively large differences in sensor view angles. The goal for this study is to check the consistency between MODIS and VIIRS ocean color data products in order to merge the products from the two sensors. We compare total radiances (Lt) at the top of atmosphere (TOA) and the ocean color (OC) data products derived with the automatic processing system (APS) from both VIIRS and MODIS data. APS was developed at the Naval Research Laboratory, Stennis Space Center (NRL/SSC). We have found that, although there are large differences between the measured radiances (Lt) of the two sensors when the sensor zenith angle differences are significant, the mean percent differences between the retrieved normalized water-leaving radiances are about 15%. The results show that the variation in satellite view zenith angles is not a main factor affecting the retrieval of ocean color data products, i.e., the atmospheric correction routine adequately removes the view-angle dependence.

High-efficiency and high-accuracy digital image correlation for three-dimensional measurement

The computational efficiency and measurement accuracy of the digital image correlation (DIC) have become more and more important in recent years. For the three-dimensional DIC (3D-DIC), these issues are much more serious. First, there are two cameras employed which increases the computational amount several times. Second, because of the differences in view angles, the must-do stereo correspondence between the left and right images is equivalently a non-uniform deformation, and cannot be weakened by increasing the sampling frequency of digital cameras. This work mainly focuses on the efficiency and accuracy of 3D-DIC. The inverse compositional Gauss–Newton algorithm (IC-GN2) with the second-order shape function is firstly proposed. Because it contains the second-order displacement gradient terms, the measurement accuracy for the non-uniform deformation thus can be improved significantly, which is typically one order higher than the first-order shape function combined with the IC-GN algorithm (IC-GN1), and 2 times faster than the second-order shape function combined with the forward additive Gauss–Newton algorithm (FA-GN2). Then, based on the features of the IC-GN1 and IC-GN2 algorithms, a high-efficiency and high-accuracy measurement strategy for 3D-DIC is proposed in the end.

Evaluation of land surface temperature and emissivities retrieved from MSG/SEVIRI data with MODIS land surface temperature and emissivity products

Land surface temperature (LST) and land surface emissivity (LSE) are two key parameters in global climate study. This article aims to cross-validate LST/LSE products retrieved from data of the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on board the first geostationary satellite, Meteosat Second Generation (MSG), with Moderate Resolution Imaging Spectroradiometer (MODIS) LST/LSE version 5 products over the Iberian Peninsula and over Egypt and the Middle East. Besides time matching, coordinate matching is another requirement of the cross-validation. An area-weighted aggregation algorithm was used to aggregate SEVIRI and MODIS LST/LSE products into the same spatial resolution. According to the quality control (QC) criterion and the view angle, the cross-validation was completed under clear-sky conditions and within a view angle difference of less than 5° for the two instruments to prevent land surface anisotropic effects. The results showed that the SEVIRI LST/LSE products are consistent with MODIS LST/LSE products and have the same trend over the two study areas during both the daytime and the night-time. The SEVIRI LST overestimates the temperature by approximately 1.0 K during the night-time and by approximately 2.0 K during the daytime compared to MODIS products over these two study areas. The SEVIRI LSE underestimates by about 0.015 in 11 μm and by about 0.025 in 12 μm over the Iberian Peninsula. However, both LSEs agree and show a difference of less than 0.01 over Egypt and the Middle East.

국립공원 집단시설지구 자연경관관리를 위한 층고규제 합리화 방안

본 연구는 국립공원 내부 혹은 경계에 연접하고 있는 집단시설지구 내의 건축물 층고 규제 기준을 정량화 된 합리적 높이 기준으로 개선하는데 목표를 두고 진행되었다. 전국 국립공원의 집단시설지구 건축물의 높이를 시뮬레이션함으로써 주요 조망점으로부터 건축물 상단을 지나는 조망선이 배후산지의 몇 부 능선까지 도달하는지를 분석하는 과정을 거쳤다. 분석 결과로 내륙의 산악형 국립공원 내부 혹은 경계에 입지하는 시설지구와 배후 산지가 있는 해안형 국립공원내의 시설지구의 경우, 3부 능선 보전을 목표로 하게 될 때 최대 허용 건축물 높이를 8.82m로 산정하는 것이 합리적이라는 결론을 얻을 수 있었다. 층수로 환산하면 3~3.5층 정도라고 할 수 있다. 이는 건축물 최대 허용 높이를 규정하는 것으로 랏지, 코티지 등을 제외한 호텔 등의 숙박시설에 적용하는 것이 바람직할 것으로 사료된다. 다만 해안해상형 중에서 배후 산지가 존재하지 않는 경우는 별도의 기준을 적용할 필요가 있다. 모든 집단시설지구에 동등한 일률적 기준을 적용하게 되면 지역 특성을 고려한 경관관리가 어렵다는 점과 조망점의 위치, 조망점 선정방법의 차이, 조망각도 차이 등의 변수에 따라 기준 적용 편차가 있을 수 있음을 고려하여야 한다. 향후 높이규정과 함께 각 지구별 경관계획에 의해 해당 지구의 자연환경에 적합한 차별화된 경관관리 전략이 필요하다. The objective of this study is to develop quantitative criteria for setting reasonable standards and regulations for building heights in collective facility districts inside national parks or those connected to their borders. Heights of all building sin collective facility districts were simulated in order to determine heights of ridge lines of sight passing the upper parts of buildings from a main view point. Where a facility's zone is located at the inside or boundary of inland mountainous national parks, and there are coastal type national parks with mountains in the background, the study recommended assigning the maximum allowable height of a building as 8.82m if national park authorities intend to preserve the ridges at three-tenths the height of a mountain. It amounts to 3 or 3.5 stories when it is converted into the number of floors. It is desirable to apply this standard to accommodations like a hotel except lodge or cottage as the maximum allowable height of a building. Nevertheless, when there aren't back mountainous areas among coastal-type national parks, there is a need for applying a separate standard. If an equal and uniform standard is applied to all collective facility districts, it becomes difficult to address local differences when managing landscape. There must be flexibility when applying a standard, depending on variables such as location of view points, differences in the methods of selection of view points, and differences in view angles, etc. Thus, there is a need for different landscape management strategies that address the unique natural environment of different zones.

An assessment of remotely sensed land surface temperature

The satellite application facility on land surface analysis (Land SAF) generates, archives, and disseminates land surface temperature (LST) in an operational basis. LST is estimated from the spinning enhanced visible and infrared imager (SEVIRI) onboard Meteosat, making use of a generalized split‐windows algorithm. Here SEVIRI LST is compared with retrievals from the moderate resolution imaging spectroradiometer (MODIS), collocated in space and time, for three 10° × 10° areas (Iberian Peninsula, Central Africa, and the Kalahari), and for six 7‐day periods between July 2005 and May 2006. Overall, SEVIRI LSTs are warmer than MODIS values, with maximum discrepancies generally observed for daytime. The mismatches between the two satellite retrievals are then analyzed in terms of (1) satellite viewing angle differences, (2) surface orography, and (3) surface type. Daytime discrepancies are strongly impacted by differential heating rates of elements within a pixel (e.g., vegetation types, bareground), leading to a relatively wide range of MODIS‐SEVIRI LST differences, with strong dependency on the MODIS view zenith angle. In contrast, average nighttime discrepancies are generally below 2°C. The intercomparison between MODIS and SEVIRI LST is complemented with in situ observations taken at Evora ground station (southwestern part of the Iberian Peninsula). The differences between ground and satellite‐derived values show high variability for daytime for both sensors, with a systematic overestimation of in situ values by SEVIRI LST. In the case of nighttime observations, both sensors tend to underestimate local measurements, with estimated bias over all events under study of −1.7°C and −2.6°C for SEVIRI and MODIS LST, respectively.

Block Bundle Adjustment of Landsat 7 ETM+ Images over Mountainous Areas

This research study showed the potential of block bundle ad- justment with nadir viewing sensor images, such as Landsat 7 ETM� . The method is based on the 3D analytical geometric model developed for multisensor images at the Canada Centre for Remote Sensing, Natural Resources Canada. Different block sizes and configurations were tested and compared using an image bundle adjustment. The different tests using 15 Landsat 7 ETMimages (five paths and three rows) ac- quired over a study site in the Canadian Rocky Mountains, showed that the same results (around 25-m errors) could be obtained with image blocks as with a single image using a largely reduced number of ground control points (GCPs). How- ever, the combined image measurement and map errors of GCPs were included in the final error budget, and the internal accuracy of the blocks should be better (around one pixel or less). The number of GCPs to be used depended mainly on the cartographic data accuracy: more GCPs than the minimum re- quired reduced the error propagation in the least-squares block bundle adjustment. In addition, tie points with a known elevation value (elevation tie points, ETPs) instead of normal tie points were used to link the adjacent images/strips (north- south and east-west) because the viewing-angle differences of overlapping images were smaller than 1° in north-south over- laps and around 10° in east-west overlaps. Better and more consistent results were also obtained using strips of images in the blocks acquired from the same orbit and date instead of using independent images. Finally, using only GCPs in the outer strips/images and ETPs in each overlap achieved the same results (25-m errors).

Compensation par segment et bloc d'images panchromatiques et multi-bandes de SPOT

This research demonstrates the potential and evaluates the conditions of experiment of SPOT image path and bloc adjustment using a 3D physical model for geometric correction of multi-source images developed at the Canada Centre for Remote Sensing. In a first step, image paths are automatically generated with the images acquired from the same orbit. Results with 11 panchromatic and 6 multiband SPOT images show that the same accuracy can be obtained with large image blocks as with a single image using a limited number of ground control points (GCPs) and tie points in all image overlaps. When the viewing angle differences of adjacent images or paths are less than 30°, the elevation should be added to these tie points, because the intersection geometry is too weak. When the viewing angle differences of adjacent images or paths are less than 6°, the final accuracy of the block can be reduced by a factor of six, and GCPs have to be added on these images to recover the initial block accuracy.

깊이정보와 블록기반매칭을 이용한 스테레오 영상의 중간영상 생성

A number of techniques have been proposed for 3D display using view-difference of two eyes. These methods do not express enough reality like real world. The display images have to change according to the position of a viewer to improve reality. In this paper, we present an approach for generating intermediate image between two different view images by applying new image interpolation algorithm The interpolation algorithm is designed to cope with complex shapes. The proposed image interpolation algorithm generates rotated image about vertical axes by any angle from base images. Each base image that was obtained from CCD camera has an view-angle difference of <TEX>$3^{\circ}C$</TEX>, <TEX>$5.5^{\circ}C$</TEX>, <TEX>$^{\circ}C$</TEX>, <TEX>$22^{\circ}C$</TEX>, and <TEX>$45^{\circ}C$</TEX>. The proposed into mediate image generation method uses the geometric analysis of image and depth information through the block-based matching method.

17.3: Color Correction in TFTLCD Displays for Compensation of Color Dependency with the Viewing Angle

AbstractMost today's twisted nematic TFTLCD displays show a color dependency with the viewing angle. This paper describes a method for compensation of the pixel color variations in these displays relative to a single viewer position. The color correction can be recomputed automatically as the viewer position changes, as long as the position is known. The method determines the color correction required for each pixel of the screen, such that a single viewer for a given position can see the color unaffected by the viewing angle differences to the screen. Color is measured in few points over the screen relative to a viewer position, and then an interpolation procedure is used to compute the color correction for each intermediate pixel, between the measured positions. The measurements for different positions of the viewer are used in a second interpolation procedure for computing color correction for intermediate position of the viewer between the measured positions. The method was experimented for portable and desktop displays. It was found that, for relative small viewing angle variations, with acceptable approximation, the color variation with the viewing angle can be modeled as variations of the transfer function. It was found that the proposed method can also be effectively used to compensate for panel uniformity.

Impact of radiance variations on satellite sensor calibration

The intercalibration of digital data from different sensors depends on systematic and random variations in factors controlling recorded radiance. Theoretical expressions are presented which describe the impact of random variations in those factors which control radiance incident on the sensor. Means of measuring or estimating the impact of random variations on intercalibration factors are discussed. Means of detecting and calibrating for systematic effects are also discussed. We consider the optical-reflective, middle-infrared, and thermal infrared regions of the spectrum. An example is presented whereby NOAA-7 and NOAA-8 advanced very high resolution radiometer (AVHRR) radiance data, obtained over the same test fields, are shown to depend on the differences in view angles used by the two satellites.