Archive for November, 2019

Thoughts on “Miller et. al – Towards an integrated science of movement”

Sunday, November 3rd, 2019

“Towards an integrated science of movement” by Miller et. al lays out the advances that have been made in the understanding of mobility and movement as a whole given the growth of location-aware technologies, which have provided much more accessible data acquisition. They are interested in synergizing the components of animal movement ecology and human mobility science to promote a science of movement.

In regards to mobile entities that are defined as “individually identifiable things that can change their location frequently with respect to time”, are there specific definitions that clearly define what “frequently in time” means? Examples have been made with birds or humans, but would trees or continental masses be considered mobiles entities as well?

It would be interesting to assess the impact of tracking location on the observations, in other words if tracking can affect the decisions made by whoever or whatever is being tracked. For example, a human who knows they are being tracked might change their trajectory solely based on the fact they do not want to potentially compromise sensitive areas or locations they visit, while an animal could behave differently if the technology used to track its movement make it more visible to predators. There is an ethical dilemma in tracking a human being without their consent, but it must be acknowledged that tracking does come with some consequences in terms of results differing from reality.

Reflecting on “Scaling Behavior of Human Mobility Distributions”

Sunday, November 3rd, 2019

Analyzing big data is an obstacle across GIS, and movement is no exception. Cutting out potentially unnecessary components of the data in order to reduce the dataset  is one way of addressing this challenge. In Paul et al.’s piece they look at how much cutting down on datasets’ time windows may affect the end distribution.

Specifically, they examine the effects of changing the spatio-temporal scale of five different movement datasets, revealing which metrics are best to compare human relationships to movement across datasets. The findings of the study, which examines GPS data from undergraduate students, graduate students, schoolchildren, and working people, reveal that changing temporal sampling periods does affect the distributions across datasets, but the extent of this change is reliant on the dataset.

After reading this piece, I would like to understand more about how researchers studying movement address privacy. I’m sure having enormous datasets of anonymized data addresses part of this issue; however, I’m sure different government agencies, organizations, corporations, etc. collecting this data have different standards regarding the importance of privacy. How strictly enforced are data privacy laws (looking at movement data specifically)? 

Thoughts on “Fisher et. al – Approaches to Uncertainty in Spatial Data”

Sunday, November 3rd, 2019

This article by Fisher et. Al clearly lays out the components and concepts that are part of spatial data uncertainty and explain solutions that have been proposed to counteract their potential consequences on data analysis and interpretation. A better understanding of what uncertainty really is helped me realize that an overwhelming majority of geographical concepts are poorly defined objects, either being vague or ambiguous.

One solution for reducing the effects of discord ambiguity, although maybe not realistic but very practical, would be to create a global lexicon that stipulates how certain statistics need to be calculated and defines concepts on a global scale. This would allow for easier comparisons between regions currently using different approaches and would uniformize the process. However, it is important to note that this could not be applied to every statistical measurement, definition or observations made given the fact there could be biases against certain regions. An example could be that a road is conceptualized differently in one part of the world when compared to another.

On the topic of data quality, the advent of geolocational technologies has propelled geospatial data to the forefront of organizations and businesses aiming to profit from their use. Without trying to be too cynical, wouldn’t private organizations have an incentive to manipulate the data quality at the detriment of others in order to benefit themselves? This is where Volunteered Geographic Information (VGI), an example being OpenStreetMap, comes into play as to balance the playing field, in this case being Google Maps.

Thoughts on “Spatial Data Quality”

Sunday, November 3rd, 2019

The authors did a good job summarizing the concepts related to spatial data quality in terms of the definitions and the types and sources of error. Although I do not completely agree with the starting statement of “geospatial data are a model of reality”, I do agree that all geospatial data are imprecise, inaccurate, out of data, and incomplete” at different levels. The question for researchers is that to what degree such impreciseness, inaccuracy, outdatedness, and incompleteness should be either accepted or rejected, and how do we assess the data quality. The authors presented the concepts of internal and external quality, where the internal quality refers to the similarity between the data produced and the perfect data should have been produced, and the external quality refers to the “fitness for use” or “fitness for purpose”. I would argue that external quality should be the metric to look at. However, as the authors stated, there is very little evaluation method for external quality. I think this is because of the “non-absoluteness” and “relativeness” properties of the external quality. It seems to be that a case-by-case assessment approach is needed depending on what the “use” is. I’m curious to know if there is a generalized way of doing this. Moreover, with geospatial data coming from different sources such as VGI, crowdsourcing, sensors, etc., the uncertainties are intensified, whereas they provide more opportunities “for use”. I think coming up with ways to assess the external quality is of vital importance.

Thoughts on “Spatial Data Quality: Concepts”

Saturday, November 2nd, 2019

This chapter begins with the quote “All models are wrong but some are useful”, which I believe sums up the article fairly succinctly, as it addresses the constant imprecise, inaccurate, incomplete, and outdated nature of GIS data. This reminds me of when we discussed non-ideal data from last week’s Openshaw (1992) paper; however, this piece explains it in much more detail than Openshaw, relating it back to external and internal data quality differences and data representation challenges. 

Since the rise in popularity of the internet and user-generated content, there is a lot more concern towards accessing data quality and accuracy. I have been conducting a bit of research on VGI, as that is my research topic, and data accountability and accuracy are huge concerns in that field. Much like differing definitions of quality given here, there is no one correct way to access accuracy. It is all reliant on the type of data being extracted and researched, and the motives for collecting such data. For instance, if a project was collecting user-generated data concerning users’ perceptions of a place, then accuracy does not matter, whereas in OpenStreetMap, for example, there is a team of moderators carefully watching and reviewing users’ inputs, as accuracy is a top priority. Thus, I think the motives for the research, specifically whether the researcher is looking for more accurate data, more precise data, or both, is a very important component to address when examining spatial data quality. 

This topic also reminds me of when we discussed open government data and how there is often not consistent data throughout each department, i.e. the formatting of the data, the original scale of the data, etc. does not usually match across departments, thus challenging the quality of the end result. I worked on a GIS project last semester analyzing water quality levels and ran into quite a few hiccups when I realized there were many months and years missing from the data sets I was trying to analyze. In hindsight, I should have examined the spatial data quality of the data I was planning to use more before starting my research.

Overall, I think this chapter does a good job of explaining the complexity of spatial data quality and the errors inherent to geospatial research.