Truth in fiction, impossible worlds, and belief revision

Franz Berto’s research was funded by the European Research Council (ERC CoG), Consolidator grant no. 681404, ‘The Logic of Conceivability’. Christopher Badura’s research was funded by the Ruhr University Research School PLUS, funded by Germany’s Excellence Initiative [DFG GSC 98/3].We present a theory of truth in fiction that improves on Lewis's [1978] ‘Analysis 2’ in two ways. First, we expand Lewis's possible worlds apparatus by adding non-normal or impossible worlds. Second, we model truth in fiction as (make-believed) belief revision via ideas from dynamic epistemic logic. We explain the major objections raised against Lewis's original view and show that our theory overcomes them.Publisher PDFPeer reviewe

The Orbital Calibration 2 (OrCa2) CubeSat Mission

The Georgia Institute of Technology (Georgia Tech), in collaboration with the Georgia Tech Research Institute (GTRI), has developed the Orbital Calibration 2 (OrCa2) mission in an effort to improve space domain awareness. OrCa2’s external panels have precise and well-characterized reflective properties that will permit various calibration activities from ground-based optical sensors, with the goal of improving the tracking and detection of resident space objects (RSOs). OrCa2 is a 12U CubeSat designed, fabricated, assembled, and tested almost entirely in-house using GT/GTRI facilities. It will be regularly observed using Georgia Tech’s Space Object Research Telescope (GT-SORT). A number of experiments can be conducted with these measurements, such as pose estimation, validation of RSO trajectory propagations with complementary ground-based laser ranging data, multi-spectral analysis, low-light detection algorithms, and validation of atmospheric scattering models. An onboard imager will serve as both a low-accuracy star camera, as well as an on-orbit optical tracking system capable of RSO streak detection, with a mission goal of gathering simultaneous ground-based and space-borne tracking data of one or more RSOs. Additionally, the OrCa2 spacecraft will host an experimental radiation dosimeter, an experimental software defined radio (SDR) receiver, and an experimental power system. OrCa2 is currently manifested to launch in Q1 2024. An overview of the design, concept of operations, and expected outcomes of the mission will be presented

Retrieval of Salt Marsh Above-ground Biomass From High-spatial Resolution Hyperspectral Imagery Using PROSAIL

Salt marsh vegetation density varies considerably on short spatial scales, complicating attempts to evaluate plant characteristics using airborne remote sensing approaches. In this study, we used a mast-mounted hyperspectral imaging system to obtain cm-scale imagery of a salt marsh chronosequence on Hog Island, VA, where the morphology and biomass of the dominant plant species, Spartina alterniflora, varies widely. The high-resolution hyperspectral imagery allowed the detailed delineation of variations in above-ground biomass, which we retrieved from the imagery using the PROSAIL radiative transfer model. The retrieved biomass estimates correlated well with contemporaneously collected in situ biomass ground truth data ( R2=0.73 ). In this study, we also rescaled our hyperspectral imagery and retrieved PROSAIL salt marsh biomass to determine the applicability of the method across spatial scales. Histograms of retrieved biomass changed considerably in characteristic marsh regions as the spatial scale of the imagery was progressively degraded. This rescaling revealed a loss of spatial detail and a shift in the mean retrieved biomass. This shift is indicative of the loss of accuracy that may occur when scaling up through a simple averaging approach that does not account for the detail found in the landscape at the natural scale of variation of the salt marsh system. This illustrated the importance of developing methodologies to appropriately scale results from very fine scale resolution up to the more coarse-scale resolutions commonly obtained in airborne and satellite remote sensing

More aboutness in imagination

In Berto's logic for aboutness in imagination, the output content of an imaginative episode must be part of the initial content of the episode (Berto, Philos Stud 175:1871–1886, 2018). This condition predicts expressions of perfectly legitimate imaginative episodes to be false. Thus, this condition is too strict. Relaxing the condition to correctly model these cases requires to consider a language with predicates and constants. The paper extends Berto's semantics for aboutness in imagination to a semantics for such a language. The new semantics models contents of formulas along the lines of Hawke's issue-based theory of topics (Hawke, Australas J Philos 96:697–723, 2017), while remaining faithful to the (in)validities discussed by Berto. Several relations between issues and topics are defined, which allow to overcome shortcomings of Hawke's initial framework. These relations are then discussed with respect to their usefulness in the truth condition for the imagination operator

Logic(s) of imagination

Wir verwenden unsere Vorstellungskraft (Imagination), um Überzeugungen zu formen oder zu rechtfertigen. Um unsere Imagination so zu verwenden, muss sie bestimmten Einschränkungen unterliegen. Wir argumentieren, dass Imagination unter anderem durch logische Gesetze und durch "aboutness" beschränkt ist. Das heißt, es spielt eine Rolle, wovon unsere Imaginationsepisoden handeln. Diese Position motiviert, dass bestimmte Schlussfolgerungen, die "vorstellen" beinhalten als gültig bzw. ungültig einzuordnen sind. Wir prüfen, inwiefern andere Logiken der Imagination diese Einordnung entsprechend unserer Intuitionen vornehmen. Im Anschluss entwickeln wir unsere eigene formale Logik der Imagination, die die Einordnung der Schlussfolgerungen adäquat vornimmt. Diese Logik umfasst drei Imaginationsoperatoren. Die formale Semantik kombiniert Ideen aus der relationalen Kripke Semantik, "branching time" Semantik für stit-Logik und "Neighbourhood" Semantik.We use our imagination to generate or justify beliefs. In order to use our imagination in this way, it must be subject to certain constraints. We argue that imagination is constrained by logical laws and "aboutness", among other things. That is, it matters what our imagination episodes are about. This position motivates that certain inferences that contain "imagine" are to be classified as valid or invalid. We examine to what extent other logics of imagination classify these inferences in line with our intuitions. We then develop our own formal logic of imagination, which adequately classifies these inferences. The logic involves three imagination operators. The formal semantics combines ideas from relational Kripke semantics, "branching time" semantics for stit logic and "neighborhood" semantics

Retrieval of Salt Marsh Above-Ground Biomass from High-Spatial Resolution Hyperspectral Imagery Using PROSAIL

Salt marsh vegetation density varies considerably on short spatial scales, complicating attempts to evaluate plant characteristics using airborne remote sensing approaches. In this study, we used a mast-mounted hyperspectral imaging system to obtain cm-scale imagery of a salt marsh chronosequence on Hog Island, VA, where the morphology and biomass of the dominant plant species, Spartina alterniflora, varies widely. The high-resolution hyperspectral imagery allowed the detailed delineation of variations in above-ground biomass, which we retrieved from the imagery using the PROSAIL radiative transfer model. The retrieved biomass estimates correlated well with contemporaneously collected in situ biomass ground truth data ( R 2 = 0.73 ). In this study, we also rescaled our hyperspectral imagery and retrieved PROSAIL salt marsh biomass to determine the applicability of the method across spatial scales. Histograms of retrieved biomass changed considerably in characteristic marsh regions as the spatial scale of the imagery was progressively degraded. This rescaling revealed a loss of spatial detail and a shift in the mean retrieved biomass. This shift is indicative of the loss of accuracy that may occur when scaling up through a simple averaging approach that does not account for the detail found in the landscape at the natural scale of variation of the salt marsh system. This illustrated the importance of developing methodologies to appropriately scale results from very fine scale resolution up to the more coarse-scale resolutions commonly obtained in airborne and satellite remote sensing

A Low-Rate Video Approach to Hyperspectral Imaging of Dynamic Scenes

The increased sensitivity of modern hyperspectral line-scanning systems has led to the development of imaging systems that can acquire each line of hyperspectral pixels at very high data rates (in the 200–400 Hz range). These data acquisition rates present an opportunity to acquire full hyperspectral scenes at rapid rates, enabling the use of traditional push-broom imaging systems as low-rate video hyperspectral imaging systems. This paper provides an overview of the design of an integrated system that produces low-rate video hyperspectral image sequences by merging a hyperspectral line scanner, operating in the visible and near infra-red, with a high-speed pan-tilt system and an integrated IMU-GPS that provides system pointing. The integrated unit is operated from atop a telescopic mast, which also allows imaging of the same surface area or objects from multiple view zenith directions, useful for bi-directional reflectance data acquisition and analysis. The telescopic mast platform also enables stereo hyperspectral image acquisition, and therefore, the ability to construct a digital elevation model of the surface. Imaging near the shoreline in a coastal setting, we provide an example of hyperspectral imagery time series acquired during a field experiment in July 2017 with our integrated system, which produced hyperspectral image sequences with 371 spectral bands, spatial dimensions of 1600 × 212, and 16 bits per pixel, every 0.67 s. A second example times series acquired during a rooftop experiment conducted on the Rochester Institute of Technology campus in August 2017 illustrates a second application, moving vehicle imaging, with 371 spectral bands, 16 bit dynamic range, and 1600 × 300 spatial dimensions every second