Technical Memorandum

Transcription

1 JB Industries Geostatistical Analysis of Spatial Data John Bull 2014

2 Introduction Finlay s Fabulous Ficiticious Fern, or Osmunda Finlayensis, is a plant species whose numbers took a sharp decline when the developments began in the vicinity of Niagara College s Glendale Campus (Smith, 2014). Fortunately, the college campus and surrounding areas are now considered biologically and ecologically suitable, and reintroduction of the fern into its natural habitat is necessary. The rarity of the fern species requires that it only be replanted in areas where suitability is extremely high, as the lack of survival for each fern could have grave consequences for the species. Weighted overlay and fuzzy overlay, are two tools that will be used to find the most suitable locations for the reintroduction of the rare fern species. By combining the strict requirements for the fern, as far as shade, slope, slope face direction, and soil, it is possible to pinpoint locations that will properly account for each of the fern s requirements. The preferred re-introduction density of one plant per 16m 2 (Smith, 2014) will also be accounted for, by performing analyses in 4m by 4m plots. 1

3 1. Study Area The area of interest for the reintroduction of Finlay s Fern, is a 1km by 2km rectangle in the vicinity of Niagara College s Glendale Campus as outlined in the terms of reference (Smith, 2014). The study area, seen in Figure 1, lies on the border of Niagara-on-the-Lake and Niagara Falls, in the eastern tip of the Niagara Peninsula. Figure 1: Area of interest for reintroduction of Finlay's Fern The small inset in Figure 1, shows the elevation changes in our area of interest. The stark elevation changes are represented in the map by changes in colour; the most distinctive of these elevation changes is in a thin strip in the middle of our area of interest, which is the Niagara Escarpment. The presence of the escarpment makes the area of interest a unique area that may have smaller plots suitable for the shy and retiring Finlay s Fern. 2

4 2. Data Data for the project was provided by the client, Mr. Ian Smith, and included mass points, breaklines, and soils data. Data was retrieved off of the Niagara College server under the following pathname: X:\GISResources\GIS-SecondSemester\GISC9308-Spatial Analysis\Assignments\Assignment2 All data was provided in the format of ESRI shapefiles, making it very easy to load the data into the computer and begin working with it. ESRI basemaps were also used in the final layouts to show the satellite imagery. As with all geospatial data, proper preprocessing was performed to ensure quality results Soils Data Soil data was the only data used for the analyses that could not be obtained from elevation measurements. The array of soils in the area of interest is represented in the soils data as polygons that each represents a different soil type. Eight different soil types were included with the soils data and are as follows: Peel Cashel Lincoln Haldimand Escarpment Beverly Toledo Not Mapped These different soil types made up 112,797 separate 4m by 4m plots; of these we can see the distribution of how many plots include which soil type in Table 1. Peel 44,104 Cashel 8,088 Lincoln 481 Haldimand 14,259 Escarpment 10,341 Beverly 6,328 Toledo 1,377 Not Mapped 27,819 Table 1: Number of 4m by 4m plots represented by each soil type Table 1 shows the ranges of soils in the area of interest as well as how prevalent they area; for example, we can see that the Peel and Not Mapped soil categories cover a large portion of the area of interest, whereas the Lincoln soils represent a very small portion of the area of interest. 3

5 The soils data were the only dataset that needed geospatial preprocessing as a positional error was evident. It was first assumed that because the soils data were projected in a different coordinate system, that reprojecting them would fix the problem, however, this did not correct the error and it therefore had to be corrected manually. Figure 2 shows how the use of satellite imagery was used to align the soils data layer to its proper geographic coordinates. Figure 2: Imagery used to align soil layers (Left Image: Raw data, Right Image: Processed data) The purple in Figure 2 represents the Not Mapped soils category whereas the red represents the Escarpment soils category. It is quite obvious using the underlying satellite imagery in the left image that the Not Mapped category should be extended down to the corner of the pond/marsh. The right image in Figure 2 represents the processed data, and aligns the soils data up far better with the underlying geography Mass Points The mass points data were the basis for the analyses in this project. Mass points data were provided in two separate shapefiles that were merged into one which covered the entire area of interest and included 20,000 points. Along with each point was an attached elevation value which was able to be used to create, or interpolate, a new, continuous surface. From this surface it is then possible to calculate hillshade, slope, and slope aspect. The mass points data were derived from the digital orthoimagery collection exercise done by the Ontario Ministry of Natural Resources in April and May of This helps to tell us two things about the dataset. Firstly, the age of the dataset required either travelling to the area of interest or to use more current imagery, such as Google Earth; this ensures that the area of interest still has similar elevation measurements and that no large land clearing projects have been done since the orthoimagery was collected. Secondly, the fact that data was collected by a government 4

6 ministry implies that proper data collection methodologies and error corrections were most likely taken place and that the data should not have any major mistakes. For this project, elevation clarification was done using Google Earth to ensure elevation measurements were roughly the same. The presence of the escarpment has a drastic effect on the distribution of elevation values in the area of interest. Figure 3 shows the almost tri-modal distribution with large peaks around 123m, 160m, and 170m. Summary for Elevation A nderson-darling Normality Test A -Squared P-V alue < Mean StDev V ariance Skew ness Kurtosis N Minimum st Q uartile Median rd Q uartile Maximum % C onfidence Interv al for Mean % C onfidence Interv al for Median % Confidence Intervals 95% C onfidence Interv al for StDev Mean Median Figure 3: Graphical summary for elevation values This data distribution corresponds closely with the area of interest as there are large areas with low elevation measurements (100m-130m) below the escarpment and there are large areas with high elevation measurements (155m-165m) on top of the escarpment. The lack of values in between the two peaks is due to sharpness of the elevation change from the escarpment. 5

7 3. Analysis The reintroduction of Finlay s Fabulous Fictitious Fern is a delicate task that requires very high precision. Areas that are highly suitable for the fern to grow need to be outlined so that reintroduction of the rare species is not wasted on unfit lands. To perform this, weighted criteria evaluations and fuzzy analysis are performed to locate ideal areas for the fern to be replanted. The fern has four major criteria which are essential to its health and growth, these include: Soil type Amount of shade/sunlight received Gradient of slope it can grow on Direction the slope is facing These four criteria are what will be used in creating areas of suitability for reintroduction of the fern. The horticultural group referred to in the terms of reference, rank these criteria based on their importance to the fern (Smith, 2014). The criteria ranking is as follows, with percent influence in parentheses: 1. Slope (47%) 2. Slope Aspect (23%) 3. Soil Type/Amount of Shade received (15%) From this, slope is the most important criterion being twice as important as slope aspect and three times as important as soil type and hillshade. Using these criteria, and their rankings as weightings, it is possible to perform weighted and fuzzy overlays to identify areas of high suitability of the reintroduction of Finlay s Fern. All analyses performed in this project were done in ESRI s ArcMap 10.1 and all maps are projected into the NAD83 UTM Zone 17N projected coordinate system, meaning all units are in meters. 6

8 3.1. Soils The soils criterion is one of the least important criteria when looking for suitable sites to reintroduce Finlay s Fern. In our suitability analyses, soils accounted for only 15% of the influence into where Finlay s Fern would be replanted; however, the limited amount of area that contained soils suitable for growing the fern still affected the result. Soils were ranked based on their suitability for the fern to grow in them, these rankings were comprised based off of the project s terms of reference and can be seen in Table 2 (Smith, 2014). 7 Soil Type Suitability Description (Smith, 2014) Ranking Escarpment Escarpment soils are best suited 2 Toledo, Cashel Toledo and Cashel soils are reasonably well suited 1 Beverly, Peel, Haldimand, Lincoln All not suited 0 Not Mapped Areas not mapped are urbanized and thus not suitable 0 Table 2: Soil suitability s and rankings The escarpment soils are clearly the best suited for the reintroduction of the fern yet they only comprise about 9% of the total soils in the area of interest which greatly reduces our area for successful reintroduction. Including the reasonably well suited soils, Toledo and Cashel, about 18% of the area of interest is reasonably well suited to replant the fern Hillshade Similarly to soils, hillshade is one of the least influential criterions in the site suitability analysis, only comprising of 15% of the influence as to where Finlay s Fern will be reintroduced. Unlike soils however, the portion of the area of interest that contained the appropriate amount of shade was quite large, covering the majority of the area. Finlay s Fern generally prefers a moderate amount of shade but it will also tolerate slightly darker and lighter conditions making it fairly suitable over a large area (Smith, 2014). The ranking criteria for hillshade are outlined in Table 3. Hillshade Range Suitability Description (Smith, 2014) Ranking Will not grow Will thrive Will not grow 0 Table 3: Hillshade suitability s and rankings All hillshade ranges are based on values for June 21 st at noon as per the terms of reference (Smith, 2014). Unlike soils, there is no grey area in the ranking for hillshade, the amount of shade either permits the growth of the fern (2), or does not allow the growth of the fern (0). The Will thrive category does dominate the area of interest, as mentioned earlier, covering approximately 85% of the study area. The large amount of suitability combined with the small influence hillshade has on the suitability output, results in hillshade having very little effect on where Finlay s Fern is reintroduced to the area of interest.

9 3.3. Slope Slope is an extremely important criterion when looking at Finlay s Fern and suitable sites for its reintroduction. Slope has the greatest influence over where the fern will be replanted at 47%, making it twice as important as the next biggest criterion. The fern itself is also only found on significant slopes, making any flat land unsuitable for the reintroduction; this greatly reduces the area that the fern could be reintroduced and thrive (Smith, 2014). The suitability ranges and ranking criteria for slope are outlined in Table 4. Slope Range Suitability Description (Smith, 2014) Ranking 0-20 No growth Sparse to full growth No growth 0 Table 4: Slope suitability s and rankings 8

10 With a requirement for such steep slopes, the only areas suitable for the reintroduction of the fern based on slope criteria alone would be directly on the escarpment or some other limited areas in the north and south parts of the image Figure 4. Figure 4: Areas with suitable slopes for Finlay's Fern 9

11 As evident in Figure 4, areas with suitable slope gradients for Finlay s Fern are very limited, covering less than 5% of the images 4m by 4m plots. The limited suitable area combined with slope accounting for 47% of the total output, greatly narrows down areas that will be suitable for the reintroduction of the fern Slope Aspect The direction a slope is facing, or the slope aspect, is the second most important criterion when looking at suitable areas for Finlay s Fern. Slope aspect accounts for 26% of the total criteria for the site suitability analyses. Slope suitability ranges and rankings are outlined in Figure 4. Slope Aspect Range Suitability Description Ranking Won t grow Will grow 2 Table 5: Slope suitability s and rankings With only two ranges, basically any slope in the range of facing west-southwest to facing north, is a suitable slope aspect for Finlay s Fern. The Niagara Escarpment also happens to fall in the appropriate aspect range, which is critical since the slope gradient criterion has limited suitable areas to primarily be on or near the escarpment. So despite approximately 46% of the study area being suitable according to the slope aspect criterion, the other criteria, particularly slope, greatly restrict this area Weighted Overlay Results The weighted overlay, or multi criteria evaluation (MCE), was the first type of site suitability analysis that was performed and is attached to this memo as Appendix C. The weighted overlay was done by simply multiplying each criterion by its influence on the suitability, and arranging the results into appropriate categories; this process is outlined in Appendix A (ESRI, 2012). In the resulting map output, areas of suitability are split into four categories including: No Growth Very Sparse Growth Reasonable Growth Full Growth The Full Growth category is representative of by far the most suitable areas to reintroduce the fern into and there is plenty of space to do so even considering the 4m by 4m density requirements. 10

12 The amount of 4m by 4m plots that fall within each suitability category are outlined in Table 6. Number of 4m by 4m Plots Suitability Category No Growth 494 Very Sparse Growth 4279 Reasonable Growth 354 Full Growth Table 6: Amount of suitable plot sizes for each suitability category From Table 6 it is seen that there are 354, 4m by 4m plots, to reintroduce the fern into extremely suitable areas; this is more than enough to accommodate the 110 Finlay s Ferns, outlined in the terms of reference, that are looking to be replanted (Smith, 2014). Areas that fall into the Full Growth category are also all located on the escarpment, meaning that no areas fell onto urban or vegetation-hindering areas and had to be removed. Three small clusters can be seen in Figure 5 that representative of the Full Growth category, all of which lie on the escarpment, and slope approximately the same way, to the northwest. Figure 5: Areas which fall in the 'Full Growth' category Outlined in the heavier weighted line in Figure 5, is the recommended location for the reintroduction of Finlay s Fern using the multi criteria evaluation. The area gives a clustered space 11

13 to introduce all 110 fern s with highly suitable characteristics such as steep sloping, slope facing northwest, appropriate amounts of sunlight, and is on the Escarpment soil type Fuzzy Overlay Results The fuzzy overlay is a method similar to the weighted overlay for finding areas that are of high suitability. Instead of reclassifying data into categories and then multiplying values by a % influence, fuzzy analysis uses statistics and user inputs to identify areas that are more suitable than others; however fuzzy overlay does not allow for the weighting of multiple criterions (ESRI, 2012). Fuzzy membership uses a specific membership type in order to determine how to sort out the data. The terms of reference provided values for these membership types for each criterion except for soils. These values are as follows (Smith, 2014): Hillshade & Slope = Gaussian Membership Type Slope Aspect = Near Membership Type The hillshade midpoint was also manually changed when performing the fuzzy membership from the default value of 54.5 to a value of 215, which better represented the midpoint of the appropriate hillshade range. The soils layer was first reclassified using the same classification scheme as the weighted overlay, and then the MSLarge membership type was used. This was done because with the soils reclassified, the more important values were higher numbers, which coincides with the MSLarge membership type. In performing the actual fuzzy overlay a gamma overlay type was applied. Originally a sum was used, as it is used in situations when the combination of multiple criterions is more important than any criterion on its own; however this is not entirely true at all times, for example the combination of hillshade and soils criterions only represent 30% of the influence whereas slope is still 47%, meaning that the combination of some criteria is not always more important. Due to this, gamma was used as it can be used as an in between from product to sum. A gamma value of 0.9 was also applied indicating the overlay should be more like the sum than the product. Similarly to the weighted overlay, the process used in the fuzzy overlay analysis has been attached as Appendix B at the end of the memo. The same four classification categories that were used in weighted overlay were again used in the fuzzy overlay; the number of 4m by 4m plots that fall into each suitability category are outlined in Table Number of 4m by 4m Plots Suitability Category 8,970 No Growth 3,729 Very Sparse Growth 4,333 Reasonable Growth 2,583 Full Growth Table 7: Amount of suitable plot sizes for each suitability category The values in Table 7 begin to show how different the two classification results are. In the weighted overlay 354, 4m by 4m plots, fell into the Full Growth category, whereas in the fuzzy overlay, we have 2,583 different plots to reintroduce the fern. The two reasons for this would be

14 how the data is arranged into classes as well as the lack of a weighting system in the fuzzy overlay. Limiting the Full Growth class, in this case, may reduce the amount of plots, but not necessarily the overall accuracy of the reintroduction. Potential areas of high suitability, or Full Growth, can once again be seen primarily on the escarpment, yet in the fuzzy overlay there is also a large strip of suitable land to the southwest of the escarpment, which can be seen in Figure 6. Figure 6: Areas of high suitability for reintroduction of Finlay's Fern The fuzzy overlay, corresponding with Table 7, has much larger areas for the Full Growth category than the weighted overlay, however the locations that were suitable in the weighed overlay also appear suitable on the fuzzy overlay. The strip to the southwest of the escarpment is highly suitable in the fuzzy overlay due to slope not having an overwhelming weighting. This thin strip is included in the Escarpment soils, and has a moderate slope, but not enough to definitively associate it as suitable to reintroduce Finlay s Fern. In all, the fuzzy overlay result gave a wider definition of areas of suitability and in combination with the weighted overlay, will be used to definitively select areas that are suitable to reintroduce Finlay s Fern. 13

15 4. Conclusions The results of both analysis techniques are similar and fairly conclusive in that the reintroduction of Finlay s Fabulous Ficiticious Fern should occur on the Niagara Escarpment. The weighted overlay gave a more precise result, limiting the amount of suitable 4m by 4m plots to 354; whereas the fuzzy overlay gave us slightly broader results, concentrating on all of the criteria equally. The combination of these two overlay s identifying a central location that will sufficiently meet all criteria for the reintroduction of Finlay s Fern. Figure 7 shows the weighted overlay placed on top of the fuzzy overlay, indicating in purple, areas that are highly suitable in both analysis techniques. Figure 7: Overlap of weighted overlay and fuzzy overlay In Figure 7, the areas of Full Growth from the fuzzy overlay are shown in blue whereas the areas of Full Growth from the weighted overlay are shown in pink, and thus areas where overlap occurs are seen in purple. The red circle outlines the predominant area of overlap and is the suggested area of reintroduction for Finlay s Fern. The area is large enough to support over 110 Finlay s Fern plants as it comprises an area of approximately 3,500m 2 ; it also lies on Escarpment 14

16 soils, has a very steep slope due to the escarpment, and faces in the west-northwest direction. The extent of this area is as follows: 649,391.8m 4,778,927.1m 4,778,849.2m 649,475.8m Other areas of suitability can be found on the map if necessary however it is suggested that the reintroduction begin in the outlined area. 15

17 Bibliography ESRI. (2012). ArcGIS 10.1 Help. Redlands, California, United States of America: ESRI. Smith, I. D. (2014, January 31). Introduction to ArcGIS Spatial Analyst Extension. Terms of Reference. Niagara-on-the-Lake, ON, Canada. 16